diff --git a/.idea/inspectionProfiles/Project_Default.xml b/.idea/inspectionProfiles/Project_Default.xml
index 0bd1d9dc2b..312610353e 100644
--- a/.idea/inspectionProfiles/Project_Default.xml
+++ b/.idea/inspectionProfiles/Project_Default.xml
@@ -867,6 +867,7 @@
     <inspection_tool class="UseOfProcessBuilder" enabled="true" level="WARNING" enabled_by_default="true" />
     <inspection_tool class="UseOfPropertiesAsHashtable" enabled="true" level="WARNING" enabled_by_default="true" />
     <inspection_tool class="UseOfSunClasses" enabled="true" level="WARNING" enabled_by_default="true" />
+    <inspection_tool class="UsePropertyAccessSyntax" enabled="true" level="WEAK WARNING" enabled_by_default="true" />
     <inspection_tool class="UtilityClass" enabled="false" level="INFO" enabled_by_default="false">
       <option name="ignorableAnnotations">
         <value />
diff --git a/buildSrc/src/main/kotlin/BuildExtensions.kt b/buildSrc/src/main/kotlin/BuildExtensions.kt
index f7a11e3e04..1c28990c57 100644
--- a/buildSrc/src/main/kotlin/BuildExtensions.kt
+++ b/buildSrc/src/main/kotlin/BuildExtensions.kt
@@ -152,6 +152,9 @@ val PluginDependenciesSpec.protobuf: PluginDependencySpec
 val PluginDependenciesSpec.prototap: PluginDependencySpec
     get() = id(ProtoTap.gradlePluginId).version(ProtoTap.version)
 
+val PluginDependenciesSpec.`spine-compiler`: PluginDependencySpec
+    get() = id(Compiler.pluginId).version(Compiler.version)
+
 val PluginDependenciesSpec.`gradle-doctor`: PluginDependencySpec
     get() = id(GradleDoctor.pluginId).version(GradleDoctor.version)
 
diff --git a/buildSrc/src/main/kotlin/io/spine/dependency/local/CoreJvmCompiler.kt b/buildSrc/src/main/kotlin/io/spine/dependency/local/CoreJvmCompiler.kt
index 2737c39cf0..b48d90e9e2 100644
--- a/buildSrc/src/main/kotlin/io/spine/dependency/local/CoreJvmCompiler.kt
+++ b/buildSrc/src/main/kotlin/io/spine/dependency/local/CoreJvmCompiler.kt
@@ -46,12 +46,12 @@ object CoreJvmCompiler {
     /**
      * The version used to in the build classpath.
      */
-    const val dogfoodingVersion = "2.0.0-SNAPSHOT.050"
+    const val dogfoodingVersion = "2.0.0-SNAPSHOT.051"
 
     /**
      * The version to be used for integration tests.
      */
-    const val version = "2.0.0-SNAPSHOT.050"
+    const val version = "2.0.0-SNAPSHOT.051"
 
     /**
      * The ID of the Gradle plugin.
diff --git a/buildSrc/src/main/kotlin/io/spine/dependency/local/Validation.kt b/buildSrc/src/main/kotlin/io/spine/dependency/local/Validation.kt
index 271ccee000..1cad8b7403 100644
--- a/buildSrc/src/main/kotlin/io/spine/dependency/local/Validation.kt
+++ b/buildSrc/src/main/kotlin/io/spine/dependency/local/Validation.kt
@@ -36,7 +36,7 @@ object Validation {
     /**
      * The version of the Validation library artifacts.
      */
-    const val version = "2.0.0-SNAPSHOT.392"
+    const val version = "2.0.0-SNAPSHOT.393"
 
     /**
      * The last version of Validation compatible with ProtoData.
diff --git a/config b/config
index dcd2cee3af..17e0dbb819 160000
--- a/config
+++ b/config
@@ -1 +1 @@
-Subproject commit dcd2cee3af82ce8e4de407801636637f7cdcef3c
+Subproject commit 17e0dbb819839d9b65b711efb085b38bcbb5eae9
diff --git a/dependencies.md b/dependencies.md
index 9faee3fde2..c9bbc99e40 100644
--- a/dependencies.md
+++ b/dependencies.md
@@ -1,6 +1,6 @@
 
 
-# Dependencies of `io.spine.tools:validation-context:2.0.0-SNAPSHOT.393`
+# Dependencies of `io.spine.tools:validation-context:2.0.0-SNAPSHOT.394`
 
 ## Runtime
 1.  **Group** : com.fasterxml.jackson. **Name** : jackson-bom. **Version** : 2.20.0.
@@ -781,16 +781,16 @@
      * **Project URL:** [http://hamcrest.org/JavaHamcrest/](http://hamcrest.org/JavaHamcrest/)
      * **License:** [BSD-3-Clause](https://raw.githubusercontent.com/hamcrest/JavaHamcrest/master/LICENSE)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.agent. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.agent. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.ant. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.ant. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.core. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.core. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.report. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.report. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
 1.  **Group** : org.jboss.forge.roaster. **Name** : roaster-api. **Version** : 2.29.0.Final.
@@ -1139,14 +1139,14 @@
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Tue Jan 20 16:21:00 WET 2026** using 
+This report was generated on **Thu Jan 29 18:44:12 WET 2026** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:validation-context-tests:2.0.0-SNAPSHOT.393`
+# Dependencies of `io.spine.tools:validation-context-tests:2.0.0-SNAPSHOT.394`
 
 ## Runtime
 1.  **Group** : com.fasterxml.jackson. **Name** : jackson-bom. **Version** : 2.20.0.
@@ -1731,14 +1731,14 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Tue Jan 20 16:21:00 WET 2026** using 
+This report was generated on **Thu Jan 29 18:44:07 WET 2026** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:validation-gradle-plugin:2.0.0-SNAPSHOT.393`
+# Dependencies of `io.spine.tools:validation-gradle-plugin:2.0.0-SNAPSHOT.394`
 
 ## Runtime
 1.  **Group** : com.fasterxml.jackson. **Name** : jackson-bom. **Version** : 2.20.0.
@@ -2433,16 +2433,16 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
      * **Project URL:** [http://hamcrest.org/JavaHamcrest/](http://hamcrest.org/JavaHamcrest/)
      * **License:** [BSD-3-Clause](https://raw.githubusercontent.com/hamcrest/JavaHamcrest/master/LICENSE)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.agent. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.agent. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.ant. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.ant. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.core. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.core. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.report. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.report. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
 1.  **Group** : org.jcommander. **Name** : jcommander. **Version** : 1.85.
@@ -2807,14 +2807,14 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Tue Jan 20 16:21:00 WET 2026** using 
+This report was generated on **Thu Jan 29 18:44:11 WET 2026** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:validation-java:2.0.0-SNAPSHOT.393`
+# Dependencies of `io.spine.tools:validation-java:2.0.0-SNAPSHOT.394`
 
 ## Runtime
 1.  **Group** : com.fasterxml.jackson. **Name** : jackson-bom. **Version** : 2.20.0.
@@ -3551,16 +3551,16 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
      * **Project URL:** [http://hamcrest.org/JavaHamcrest/](http://hamcrest.org/JavaHamcrest/)
      * **License:** [BSD-3-Clause](https://raw.githubusercontent.com/hamcrest/JavaHamcrest/master/LICENSE)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.agent. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.agent. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.ant. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.ant. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.core. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.core. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.report. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.report. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
 1.  **Group** : org.jcommander. **Name** : jcommander. **Version** : 1.85.
@@ -3901,14 +3901,14 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Tue Jan 20 16:21:00 WET 2026** using 
+This report was generated on **Thu Jan 29 18:44:11 WET 2026** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:validation-java-bundle:2.0.0-SNAPSHOT.393`
+# Dependencies of `io.spine.tools:validation-java-bundle:2.0.0-SNAPSHOT.394`
 
 ## Runtime
 1.  **Group** : com.google.auto.service. **Name** : auto-service-annotations. **Version** : 1.1.1.
@@ -3971,14 +3971,14 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Tue Jan 20 16:21:00 WET 2026** using 
+This report was generated on **Thu Jan 29 18:44:07 WET 2026** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine:validation-jvm-runtime:2.0.0-SNAPSHOT.393`
+# Dependencies of `io.spine:validation-jvm-runtime:2.0.0-SNAPSHOT.394`
 
 ## Runtime
 1.  **Group** : com.google.code.findbugs. **Name** : jsr305. **Version** : 3.0.2.
@@ -4465,16 +4465,16 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
      * **Project URL:** [http://hamcrest.org/JavaHamcrest/](http://hamcrest.org/JavaHamcrest/)
      * **License:** [BSD-3-Clause](https://raw.githubusercontent.com/hamcrest/JavaHamcrest/master/LICENSE)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.agent. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.agent. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.ant. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.ant. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.core. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.core. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.report. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.report. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
 1.  **Group** : org.jcommander. **Name** : jcommander. **Version** : 1.85.
@@ -4811,14 +4811,14 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Tue Jan 20 16:21:00 WET 2026** using 
+This report was generated on **Thu Jan 29 18:44:11 WET 2026** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:validation-ksp:2.0.0-SNAPSHOT.393`
+# Dependencies of `io.spine.tools:validation-ksp:2.0.0-SNAPSHOT.394`
 
 ## Runtime
 1.  **Group** : com.google.auto.service. **Name** : auto-service-annotations. **Version** : 1.1.1.
@@ -5368,16 +5368,16 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
      * **Project URL:** [http://hamcrest.org/JavaHamcrest/](http://hamcrest.org/JavaHamcrest/)
      * **License:** [BSD-3-Clause](https://raw.githubusercontent.com/hamcrest/JavaHamcrest/master/LICENSE)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.agent. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.agent. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.ant. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.ant. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.core. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.core. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
-1.  **Group** : org.jacoco. **Name** : org.jacoco.report. **Version** : 0.8.13.
+1.  **Group** : org.jacoco. **Name** : org.jacoco.report. **Version** : 0.8.14.
      * **License:** [EPL-2.0](https://www.eclipse.org/legal/epl-2.0/)
 
 1.  **Group** : org.jcommander. **Name** : jcommander. **Version** : 1.85.
@@ -5747,14 +5747,14 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Tue Jan 20 16:21:00 WET 2026** using 
+This report was generated on **Thu Jan 29 18:44:11 WET 2026** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:validation-consumer:2.0.0-SNAPSHOT.393`
+# Dependencies of `io.spine.tools:validation-consumer:2.0.0-SNAPSHOT.394`
 
 ## Runtime
 1.  **Group** : com.fasterxml.jackson. **Name** : jackson-bom. **Version** : 2.20.0.
@@ -6345,14 +6345,14 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Tue Jan 20 16:21:00 WET 2026** using 
+This report was generated on **Thu Jan 29 18:44:07 WET 2026** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:validation-consumer-dependency:2.0.0-SNAPSHOT.393`
+# Dependencies of `io.spine.tools:validation-consumer-dependency:2.0.0-SNAPSHOT.394`
 
 ## Runtime
 1.  **Group** : com.google.code.findbugs. **Name** : jsr305. **Version** : 3.0.2.
@@ -6863,14 +6863,14 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Tue Jan 20 16:21:00 WET 2026** using 
+This report was generated on **Thu Jan 29 18:44:08 WET 2026** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:validation-extensions:2.0.0-SNAPSHOT.393`
+# Dependencies of `io.spine.tools:validation-extensions:2.0.0-SNAPSHOT.394`
 
 ## Runtime
 1.  **Group** : com.fasterxml.jackson. **Name** : jackson-bom. **Version** : 2.20.0.
@@ -7554,14 +7554,14 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Tue Jan 20 16:21:00 WET 2026** using 
+This report was generated on **Thu Jan 29 18:44:08 WET 2026** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:validation-runtime:2.0.0-SNAPSHOT.393`
+# Dependencies of `io.spine.tools:validation-runtime:2.0.0-SNAPSHOT.394`
 
 ## Runtime
 1.  **Group** : com.google.code.findbugs. **Name** : jsr305. **Version** : 3.0.2.
@@ -8183,14 +8183,14 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Tue Jan 20 16:21:00 WET 2026** using 
+This report was generated on **Thu Jan 29 18:44:08 WET 2026** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:validation-validating:2.0.0-SNAPSHOT.393`
+# Dependencies of `io.spine.tools:validation-validating:2.0.0-SNAPSHOT.394`
 
 ## Runtime
 1.  **Group** : com.google.code.findbugs. **Name** : jsr305. **Version** : 3.0.2.
@@ -8855,14 +8855,14 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Tue Jan 20 16:21:00 WET 2026** using 
+This report was generated on **Thu Jan 29 18:44:08 WET 2026** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:validation-validator:2.0.0-SNAPSHOT.393`
+# Dependencies of `io.spine.tools:validation-validator:2.0.0-SNAPSHOT.394`
 
 ## Runtime
 1.  **Group** : com.fasterxml.jackson. **Name** : jackson-bom. **Version** : 2.20.0.
@@ -9613,14 +9613,14 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Tue Jan 20 16:21:00 WET 2026** using 
+This report was generated on **Thu Jan 29 18:44:08 WET 2026** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:validation-validator-dependency:2.0.0-SNAPSHOT.393`
+# Dependencies of `io.spine.tools:validation-validator-dependency:2.0.0-SNAPSHOT.394`
 
 ## Runtime
 1.  **Group** : com.google.code.findbugs. **Name** : jsr305. **Version** : 3.0.2.
@@ -9890,14 +9890,14 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Tue Jan 20 16:21:00 WET 2026** using 
+This report was generated on **Thu Jan 29 18:44:07 WET 2026** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
 
 
 
 
-# Dependencies of `io.spine.tools:validation-vanilla:2.0.0-SNAPSHOT.393`
+# Dependencies of `io.spine.tools:validation-vanilla:2.0.0-SNAPSHOT.394`
 
 ## Runtime
 1.  **Group** : com.google.code.findbugs. **Name** : jsr305. **Version** : 3.0.2.
@@ -10248,6 +10248,6 @@ This report was generated on **Tue Jan 20 16:21:00 WET 2026** using
 
 The dependencies distributed under several licenses, are used according their commercial-use-friendly license.
 
-This report was generated on **Tue Jan 20 16:21:00 WET 2026** using 
+This report was generated on **Thu Jan 29 18:44:07 WET 2026** using 
 [Gradle-License-Report plugin](https://github.com/jk1/Gradle-License-Report) by Evgeny Naumenko, licensed under 
 [Apache 2.0 License](https://github.com/jk1/Gradle-License-Report/blob/master/LICENSE).
\ No newline at end of file
diff --git a/docs/STRUCTURE.md b/docs/STRUCTURE.md
new file mode 100644
index 0000000000..2ec5a14bcb
--- /dev/null
+++ b/docs/STRUCTURE.md
@@ -0,0 +1,175 @@
+# Structuring repositories for Hugo documentation using Go modules
+
+This document describes the **recommended repository layout and Hugo
+Module mount strategy** for building modular documentation where:
+
+-   The **main site** assembles documentation from multiple repositories
+-   Each framework/library keeps **all documentation isolated under
+    `docs/`**
+-   Hugo Modules (Go modules) are used for versioning and composition
+
+------------------------------------------------------------------------
+
+## High-level architecture
+
+-   **Main site repository**
+    -   Hugo site that assembles all documentation
+    -   Imports documentation modules only
+-   **Documentation provider repositories** (framework, libraries)
+    -   Each repo exposes its documentation as a **Hugo Module**
+    -   All doc-related files live under `docs/`
+
+Each `docs/` directory is:
+ - a **Go module root** (`go.mod`)
+ - a **Hugo project root** (`hugo.yaml`)
+
+------------------------------------------------------------------------
+
+## Main site repository
+
+    main-site/
+      go.mod
+      hugo.yaml
+      content/
+      layouts/
+      assets/
+
+### hugo.yaml
+
+``` yaml
+module:
+  imports:
+    - path: github.com/your-org/framework/docs
+    - path: github.com/your-org/lib-foo/docs
+    - path: github.com/your-org/lib-bar/docs
+```
+
+------------------------------------------------------------------------
+
+## Framework documentation repository
+
+    framework/
+      docs/
+        go.mod
+        go.sum
+        hugo.yaml
+        content/
+          framework/
+            _index.md
+        layouts/
+        assets/
+
+### docs/go.mod
+
+``` go
+module github.com/your-org/framework/docs
+go 1.22
+```
+
+### docs/hugo.yaml
+
+``` yaml
+module:
+  mounts:
+    - source: content
+      target: content/framework
+    - source: layouts
+      target: layouts
+    - source: assets
+      target: assets
+```
+
+------------------------------------------------------------------------
+
+## Library documentation repository (example: lib-foo)
+
+    lib-foo/
+      docs/
+        go.mod
+        hugo.yaml
+        content/
+          libraries/
+            foo/
+              _index.md
+
+### docs/go.mod
+
+``` go
+module github.com/your-org/lib-foo/docs
+go 1.22
+```
+
+### docs/hugo.yaml
+
+``` yaml
+module:
+  mounts:
+    - source: content
+      target: content/libraries/foo
+    - source: layouts
+      target: layouts
+    - source: assets
+      target: assets
+```
+
+------------------------------------------------------------------------
+
+## Content conventions
+ *	Always mount into namespaced sections:
+ *	`content/framework/...`
+ *	`content/libraries/<libname>/...`
+ *	Use `_index.md` at section roots to create proper landing pages
+ *	Avoid mounting directly to `content/` without a subdirectory
+
+------------------------------------------------------------------------
+
+## Optional: shared documentation UI module
+
+For shared shortcodes, partials, and styling:
+
+    docs-ui/
+    go.mod
+    hugo.yaml
+    layouts/
+    shortcodes/
+    partials/
+    assets/
+
+**docs-ui/hugo.yaml:**
+
+```yaml
+module:
+  mounts:
+  - source: layouts
+    target: layouts
+  - source: assets
+    target: assets
+```
+Import this module before content modules in the main site.
+
+------------------------------------------------------------------------
+
+## Local development
+
+Run documentation standalone from a repo:
+
+    cd framework
+    hugo server --source docs
+
+For multi-repo development, consider a go.work file to use local checkouts instead of remote module versions.
+
+------------------------------------------------------------------------
+
+## Key rules to follow
+ * docs/ is the only Hugo + Go module root in doc-providing repos
+ * Each docs module defines its own mounts
+ * The main site only imports modules
+ * Mount targets must be unique and namespaced
+ * Commit both go.mod and go.sum for reproducible builds
+
+------------------------------------------------------------------------
+
+## References
+ * Hugo Modules overview: https://gohugo.io/hugo-modules/
+ * Hugo module configuration: https://gohugo.io/configuration/module/
+ * Go modules reference: https://go.dev/ref/mod
diff --git a/docs/ToC.md b/docs/ToC.md
deleted file mode 100644
index 87515e2df0..0000000000
--- a/docs/ToC.md
+++ /dev/null
@@ -1,96 +0,0 @@
-# Spine Validation — Table of Contents
-
-## 0. Introduction
-- [Overview](00-intro/index.md)
-- [Target Audience](00-intro/target-audience.md)
-- [Philosophy](00-intro/philosophy.md)
-
-## 1. Getting Started
-- [Getting Started](01-getting-started/index.md)
-- [Installation](01-getting-started/installation.md)
-- [Your First Validated Model](01-getting-started/first-model.md)
-- [Validation Workflow](01-getting-started/workflow.md)
-
-## 2. Concepts
-- [Concepts Overview](02-concepts/index.md)
-- [Validation Options Overview](02-concepts/options-overview.md)
-- [The Validation Engine](02-concepts/validation-engine.md)
-- [Integration with Protobuf & Compiler](02-concepts/protobuf-integration.md)
-
-## 3. Built-in Validation Options
-- [Built-in Options Overview](03-built-in-options/index.md)
-
-### 3.1. Field Constraints
-- [Overview](03-built-in-options/fields/index.md)
-- [required](03-built-in-options/fields/required.md)
-- [pattern](03-built-in-options/fields/pattern.md)
-- [min/max](03-built-in-options/fields/min-max.md)
-- [range](03-built-in-options/fields/range.md)
-- [length/size](03-built-in-options/fields/length-size.md)
-- [unique](03-built-in-options/fields/unique.md)
-
-### 3.2. Collection Constraints
-- [Overview](03-built-in-options/collections/index.md)
-- [non_empty](03-built-in-options/collections/non-empty.md)
-- [distinct](03-built-in-options/collections/distinct.md)
-- [collection size](03-built-in-options/collections/collection-size.md)
-
-### 3.3. String Constraints
-- [Overview](03-built-in-options/strings/index.md)
-- [Advanced Patterns](03-built-in-options/strings/pattern-advanced.md)
-- [email](03-built-in-options/strings/email.md)
-- [hostname](03-built-in-options/strings/hostname.md)
-- [uri](03-built-in-options/strings/uri.md)
-
-### 3.4. Numeric Constraints
-- [Overview](03-built-in-options/numbers/index.md)
-- [Numeric Bounds](03-built-in-options/numbers/numeric-bounds.md)
-
-### 3.5. Temporal Constraints
-- [Overview](03-built-in-options/temporal/index.md)
-- [when](03-built-in-options/temporal/when.md)
-- [Timestamp & Duration](03-built-in-options/temporal/timestamp-duration.md)
-
-### 3.6. Message-level Constraints
-- [Overview](03-built-in-options/message/index.md)
-- [required_for](03-built-in-options/message/required-for.md)
-- [Nested Validation](03-built-in-options/message/nested-validation.md)
-- [Cross-field Validation](03-built-in-options/message/cross-field.md)
-
-## 4. Using Validation in Code
-- [Overview](04-using-validation/index.md)
-- [Validating Messages](04-using-validation/validating-messages.md)
-- [Handling Errors](04-using-validation/handling-errors.md)
-- [Kotlin Usage](04-using-validation/kotlin-usage.md)
-- [Framework Integration](04-using-validation/framework-integration.md)
-
-## 5. Configuration & Tooling
-- [Overview](05-configuration/index.md)
-- [Compiler Configuration](05-configuration/compiler.md)
-- [Library Modules](05-configuration/modules.md)
-- [Debugging Generated Code](05-configuration/debugging.md)
-
-## 6. Extending Validation
-- [Overview](06-extending/index.md)
-- [Architecture](06-extending/architecture.md)
-- [Custom Validation Options](06-extending/custom-options.md)
-- [Custom Runtime Validators](06-extending/custom-runtime-validators.md)
-
-## 7. Recipes (Cookbook)
-- [Overview](07-recipes/index.md)
-- [Domain IDs](07-recipes/domain-ids.md)
-- [Common Cases](07-recipes/common-cases.md)
-- [Temporal Logic](07-recipes/temporal-logic.md)
-- [Cross-field Logic](07-recipes/cross-field-logic.md)
-- [API Validation](07-recipes/api-validation.md)
-
-## 8. Migration Guide
-- [Overview](08-migration/index.md)
-- [Migrating from `spine.base` Validation](08-migration/from-spine-base.md)
-- [Version Changes](08-migration/version-changes.md)
-
-## 9. Reference
-- [Reference Overview](09-reference/index.md)
-- [List of Validation Options](09-reference/options.md)
-- [Java/Kotlin API Index](09-reference/api.md)
-- [Glossary](09-reference/glossary.md)
diff --git a/docs/_code/first-model/build.gradle.kts b/docs/_code/first-model/build.gradle.kts
new file mode 100644
index 0000000000..63d5ae9c96
--- /dev/null
+++ b/docs/_code/first-model/build.gradle.kts
@@ -0,0 +1,64 @@
+import io.spine.dependency.lib.Guava
+import io.spine.dependency.local.Base
+import io.spine.gradle.repo.standardToSpineSdk
+
+/*
+ * Copyright 2026, TeamDev. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Redistribution and use in source and/or binary forms, with or without
+ * modification, must retain the above copyright notice and the following
+ * disclaimer.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+buildscript {
+    standardSpineSdkRepositories()
+    dependencies {
+        classpath(io.spine.dependency.local.Compiler.pluginLib)
+    }
+}
+
+plugins {
+    `java-library`
+    kotlin("jvm")
+    id("com.google.protobuf")
+    `spine-compiler`
+    id("io.spine.validation")
+}
+
+group = "io.spine.docs"
+version = "2.0.0"
+
+repositories {
+    mavenLocal()
+    standardToSpineSdk()
+}
+
+dependencies {
+    testImplementation(kotlin("test"))
+}
+
+kotlin {
+    jvmToolchain(17)
+}
+
+tasks.test {
+    useJUnitPlatform()
+}
diff --git a/docs/_code/first-model/buildSrc b/docs/_code/first-model/buildSrc
new file mode 120000
index 0000000000..f59909572b
--- /dev/null
+++ b/docs/_code/first-model/buildSrc
@@ -0,0 +1 @@
+/Users/sanders/Projects/Spine/validation/buildSrc
\ No newline at end of file
diff --git a/docs/_code/first-model/gradle.properties b/docs/_code/first-model/gradle.properties
new file mode 120000
index 0000000000..e98d4551a2
--- /dev/null
+++ b/docs/_code/first-model/gradle.properties
@@ -0,0 +1 @@
+/Users/sanders/Projects/Spine/validation/gradle.properties
\ No newline at end of file
diff --git a/docs/_code/first-model/gradlew b/docs/_code/first-model/gradlew
new file mode 120000
index 0000000000..b1781d235f
--- /dev/null
+++ b/docs/_code/first-model/gradlew
@@ -0,0 +1 @@
+/Users/sanders/Projects/Spine/validation/gradlew
\ No newline at end of file
diff --git a/docs/_code/first-model/gradlew.bat b/docs/_code/first-model/gradlew.bat
new file mode 120000
index 0000000000..1ed85a1435
--- /dev/null
+++ b/docs/_code/first-model/gradlew.bat
@@ -0,0 +1 @@
+/Users/sanders/Projects/Spine/validation/gradlew.bat
\ No newline at end of file
diff --git a/proto/configuration/build.gradle.kts b/docs/_code/first-model/settings.gradle.kts
similarity index 79%
rename from proto/configuration/build.gradle.kts
rename to docs/_code/first-model/settings.gradle.kts
index 3fc1917dd9..4379439985 100644
--- a/proto/configuration/build.gradle.kts
+++ b/docs/_code/first-model/settings.gradle.kts
@@ -1,5 +1,5 @@
 /*
- * Copyright 2024, TeamDev. All rights reserved.
+ * Copyright 2026, TeamDev. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -24,18 +24,13 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-import io.spine.dependency.local.Compiler
+rootProject.name = "first-model"
 
-plugins {
-    `build-proto-model`
+pluginManagement {
+    repositories {
+        gradlePluginPortal()
+        mavenLocal()
+    }
 }
 
-dependencies {
-    api(Compiler.api)
-}
-
-afterEvaluate {
-    val kspKotlin by tasks.getting
-    val launchSpineCompiler by tasks.getting
-    kspKotlin.dependsOn(launchSpineCompiler)
-}
+includeBuild("../../../")
diff --git a/docs/_code/first-model/src/main/proto/spine/validation/docs/first_model/bank_card.proto b/docs/_code/first-model/src/main/proto/spine/validation/docs/first_model/bank_card.proto
new file mode 100644
index 0000000000..ce5bc4d4c2
--- /dev/null
+++ b/docs/_code/first-model/src/main/proto/spine/validation/docs/first_model/bank_card.proto
@@ -0,0 +1,33 @@
+syntax = "proto3";
+
+package spine.validation.docs.first_model;
+
+import "spine/options.proto";
+
+option (type_url_prefix) = "type.spine.io";
+option java_package = "io.spine.validation.docs.firstmodel";
+option java_multiple_files = true;
+
+// Provides bank card information with validation rules.
+//
+// The digits of the card are simplified for the sake of the example.
+//
+message BankCard {
+
+    // Must be present and match a simple card pattern.
+    string digits = 1 [
+        (required) = true,
+        (pattern).regex = "^\\d{4}(?: \\d{4}){3}"
+    ];
+
+    // Must be present and contain at least 4 Latin letters or spaces.
+    string owner = 2 [
+        (required) = true,
+        (pattern).regex = "^[A-Z](?:[A-Za-z ]{2,}[A-Za-z])$"
+    ];
+
+    // All tags must be unique. Tags are optional.
+    repeated string tags = 3 [
+        (distinct) = true
+    ];
+}
diff --git a/docs/_code/first-model/src/test/java/io/spine/validation/docs/firstmodel/BankCardTest.java b/docs/_code/first-model/src/test/java/io/spine/validation/docs/firstmodel/BankCardTest.java
new file mode 100644
index 0000000000..a31d505097
--- /dev/null
+++ b/docs/_code/first-model/src/test/java/io/spine/validation/docs/firstmodel/BankCardTest.java
@@ -0,0 +1,86 @@
+/*
+ * Copyright 2026, TeamDev. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Redistribution and use in source and/or binary forms, with or without
+ * modification, must retain the above copyright notice and the following
+ * disclaimer.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package io.spine.validation.docs.firstmodel;
+
+import io.spine.validation.ValidationException;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+@DisplayName("`BankCard` should")
+class BankCardTest {
+
+    @Test
+    @DisplayName("throw `ValidationException` if digits are invalid")
+    void invalidDigits() {
+        assertThrows(ValidationException.class, () ->
+            BankCard.newBuilder()
+                .setDigits("invalid")
+                .setOwner("ALEX SMITH")
+                .build()
+        );
+    }
+
+    @Test
+    @DisplayName("throw `ValidationException` if owner is invalid")
+    void invalidOwner() {
+        assertThrows(ValidationException.class, () ->
+            BankCard.newBuilder()
+                .setDigits("1234 5678 1234 5678")
+                .setOwner("Al")
+                .build()
+        );
+    }
+
+    @Test
+    @DisplayName("throw `ValidationException` if tags are not distinct")
+    void duplicateTags() {
+        assertThrows(ValidationException.class, () ->
+            BankCard.newBuilder()
+                .setDigits("1234 5678 1234 5678")
+                .setOwner("ALEX SMITH")
+                .addTags("personal")
+                .addTags("personal")
+                .build()
+        );
+    }
+
+    @Test
+    @DisplayName("be built if all fields are valid")
+    void validCard() {
+        assertDoesNotThrow(() ->
+            BankCard.newBuilder()
+                .setDigits("1234 5678 1234 5678")
+                .setOwner("ALEX SMITH")
+                .addTags("personal")
+                .addTags("travel")
+                .build()
+        );
+    }
+}
diff --git a/docs/_code/first-model/src/test/kotlin/io/spine/validation/docs/firstmodel/BankCardKtTest.kt b/docs/_code/first-model/src/test/kotlin/io/spine/validation/docs/firstmodel/BankCardKtTest.kt
new file mode 100644
index 0000000000..8587787d45
--- /dev/null
+++ b/docs/_code/first-model/src/test/kotlin/io/spine/validation/docs/firstmodel/BankCardKtTest.kt
@@ -0,0 +1,85 @@
+/*
+ * Copyright 2026, TeamDev. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Redistribution and use in source and/or binary forms, with or without
+ * modification, must retain the above copyright notice and the following
+ * disclaimer.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package io.spine.validation.docs.firstmodel
+
+import io.spine.validation.ValidationException
+import org.junit.jupiter.api.DisplayName
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
+import org.junit.jupiter.api.Assertions.assertDoesNotThrow
+
+@DisplayName("`BankCard`in Kotlin should")
+class BankCardKtTest {
+
+    @Test
+    @DisplayName("throw `ValidationException` if digits are invalid")
+    fun invalidDigits() {
+        assertThrows<ValidationException> {
+            bankCard {
+                digits = "invalid"
+                owner = "ALEX SMITH"
+            }
+        }
+    }
+
+    @Test
+    @DisplayName("throw `ValidationException` if owner is invalid")
+    fun invalidOwner() {
+        assertThrows<ValidationException> {
+            bankCard {
+                digits = "1234 5678 1234 5678"
+                owner = "Al"
+            }
+        }
+    }
+
+    @Test
+    @DisplayName("throw `ValidationException` if tags are not distinct")
+    fun duplicateTags() {
+        assertThrows<ValidationException> {
+            bankCard {
+                digits = "1234 5678 1234 5678"
+                owner = "ALEX SMITH"
+                tags.add("personal")
+                tags.add("personal")
+            }
+        }
+    }
+
+    @Test
+    @DisplayName("be built if all fields are valid")
+    fun validCard() {
+        assertDoesNotThrow {
+            bankCard {
+                digits = "1234 5678 1234 5678"
+                owner = "ALEX SMITH"
+                tags.add("personal")
+                tags.add("travel")
+            }
+        }
+    }
+}
diff --git a/docs/_options/options.proto b/docs/_options/options.proto
new file mode 100644
index 0000000000..31f02bfa67
--- /dev/null
+++ b/docs/_options/options.proto
@@ -0,0 +1,1566 @@
+/*
+ * Copyright 2024, TeamDev. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Redistribution and use in source and/or binary forms, with or without
+ * modification, must retain the above copyright notice and the following
+ * disclaimer.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+syntax = "proto3";
+
+// API Note on Packaging
+// ---------------------
+// We do not define the package for this file to allow shorter options for user-defined types.
+// This allows to write:
+//
+//     option (internal) = true;
+//
+// instead of:
+//
+//      option (spine.base.internal) = true;
+//
+
+// Custom Type Prefix Option
+// -------------------------
+// The custom `type_url_prefix` option allows to define specify custom type URL prefix for messages
+// defined in a proto file. This option is declared in this file. Other proto files must import
+// `options.proto` to be able to specify custom type URL prefix.
+//
+// It is recommended that the import statement is provided before the line with `type_url_prefix`
+// option to make it obvious that custom option is defined in the imported file.
+//
+// For example:
+//
+// syntax = "proto3";
+//
+// package my.package;
+//
+// import "spine/options.proto";
+//
+// option (type_url_prefix) = "type.example.org";
+//
+
+option (type_url_prefix) = "type.spine.io";
+option java_multiple_files = true;
+option java_outer_classname = "OptionsProto";
+option java_package = "io.spine.option";
+
+import "google/protobuf/descriptor.proto";
+
+//
+// Reserved Range of Option Field Numbers
+// --------------------------------------
+// Spine Options use the range of option field numbers from the internal range reserved for
+// individual organizations. For details of custom Protobuf options and this range please see:
+//
+//      https://developers.google.com/protocol-buffers/docs/proto#customoptions
+//
+// The whole range reserved for individual organizations is 50000-99999.
+// The range used by Spine Options is 73812-75000.
+// In order to prevent number collision with custom options used by a project based on Spine,
+// numbers for custom options defined in this project should be in the range 50000-73811 or
+// 75001-99999.
+//
+
+extend google.protobuf.FieldOptions {
+
+    // Field Validation Constraints
+    //-----------------------------
+    // For constraints defined via message-based types, please see documentation of corresponding
+    // message types.
+    //
+
+    // The option to mark a field as required.
+    //
+    // When this option is set:
+    //
+    // 1. For message or enum fields, the field must be set to a non-default instance.
+    // 2. For `string` and `bytes` fields, the value must be set to a non-empty string or an array.
+    // 3. For repeated fields and maps, at least one element must be present.
+    //
+    // Other field types are not supported by the option.
+    //
+    // Unlike the `required` keyword in Protobuf 2, this option does not affect message
+    // serialization or deserialization. Even if a message content violates the requirement
+    // set by the option, it would still be a valid message for the Protobuf library.
+    //
+    // Example: Using `(required)` field validation constraint.
+    //
+    //     message MyOuterMessage {
+    //         MyMessage field = 1 [(required) = true];
+    //     }
+    //
+    bool required = 73812;
+
+    // See `IfMissingOption`
+    IfMissingOption if_missing = 73813;
+
+    // Reserved 73814 and 73815 for deleted options `decimal_max` and `decimal_min`.
+
+    // A higher boundary to the range of values of a number.
+    MaxOption max = 73816;
+
+    // A lower boundary to the range of values of a number.
+    MinOption min = 73817;
+
+    // 73818 reserved for the (digits) option.
+
+    // 73819 reserved for the (when) option.
+
+    // See `PatternOption`.
+    PatternOption pattern = 73820;
+
+    // Enables in-depth validation for fields that refer to a message.
+    //
+    // This option applies only to fields that reference a message:
+    //
+    //   1. Singular message fields.
+    //   2. Repeated fields of message types.
+    //   3. Map fields with message types as values.
+    //
+    // When set to `true`, the field is valid only if its value satisfies the validation
+    // constraints defined in the corresponding message type:
+    //
+    //   1. For singular message fields: the message must meet its constraints.
+    //
+    //      Note: default instances are considered valid even if the message has required fields.
+    //      In such cases, it is unclear whether the field is set with an invalid instance or
+    //      simply unset.
+    //
+    //      Example:
+    //
+    //      ```
+    //      // Note that the default instance of `Address` is not valid because the `value` field
+    //      // is mandatory.
+    //      message Address {
+    //          string value = 1 [(required) = true];
+    //      }
+    //
+    //      // However, the default instance of `Address` in `Student.address` is valid, despite
+    //      // having `(validate)` constraint that forces the message to meet its constraints.
+    //      // Since the `address` field is optional for `Student`, `(validate)` would allow
+    //      // default instances for this field treating them as "no value set".
+    //      message Student {
+    //          Address address = 1 [(validate) = true]; // implicit `(required) = false`.
+    //      }
+    //
+    //      // Make the validated field required to avoid this behavior. In this case, `(validate)`
+    //      // continues to bypass default instances, but the `(required)` option will report them.
+    //      message Student {
+    //          Address address = 1 [(validate) = true, (required) = true];
+    //      }
+    //      ```
+    //
+    //   2. For repeated fields: every element in the repeated field must meet the constraints
+    //      of its message type.
+    //
+    //      Example:
+    //
+    //      ```
+    //      // Note that the default instance of `PhoneNumber` is not valid because the `value`
+    //      // field is mandatory.
+    //      message PhoneNumber {
+    //          string value = 1 [(required) = true, (pattern).regex = "^\+?[0-9\s\-()]{1,30}$"];
+    //      }
+    //
+    //      // In contrast to singular fields, the default instances in `repeated` will also be
+    //      // reported by the `(validate)` constraint, with those that do not match the pattern.
+    //      message Student {
+    //          repeated PhoneNumber number = 1 [(validate) = true];
+    //      }
+    //      ```
+    //
+    //   3. For map fields: each value in the map must meet the constraints of message type.
+    //      Note: Protobuf does not allow messages to be used as map keys.
+    //
+    //      Example:
+    //
+    //      ```
+    //      // Note that the default instance of `PhoneNumber` is not valid because the `value`
+    //      // field is mandatory.
+    //      message PhoneNumber {
+    //          string value = 1 [(required) = true, (pattern).regex = "^\+?[0-9\s\-()]{1,30}$"];
+    //      }
+    //
+    //      // In contrast to singular fields, the default instances in `map` values will also be
+    //      // reported by the `(validate)` constraint, with those that do not match the pattern.
+    //      message Contacts {
+    //          map<string, PhoneNumber> map = 1 [(validate) = true];
+    //      }
+    //      ```
+    //
+    // If the field contains `google.protobuf.Any`, the option will first attempt to unpack
+    // the enclosed message, and only then validate it. However, unpacking is not always possible:
+    //
+    //   1. The default instance of `Any` is always valid because there is nothing to unpack
+    //      and validate.
+    //   2. Instances with type URLs that are unknown to the application are also valid.
+    //
+    //      Unpacking requires a corresponding Java class to deserialize the message, but if
+    //      the application does not recognize the type URL, it has no way to determine which
+    //      class to use.
+    //
+    //      Such may happen when the packed message comes from a newer app version, an external
+    //      system, or is simply not included in the application’s dependencies.
+    //
+    bool validate = 73821;
+
+    // See `IfInvalidOption`.
+    IfInvalidOption if_invalid = 73822 [deprecated = true];
+
+    // See `GoesOption`.
+    GoesOption goes = 73823;
+
+    // Indicates that a field can only be set once.
+    //
+    // This option allows the target field to accept assignments only if one of the following
+    // conditions is met:
+    //
+    // 1. The current field value is the default for its type.
+    //    Refer to the official docs on default values: https://protobuf.dev/programming-guides/proto3/#default.
+    // 2. The current field value equals to the proposed new value.
+    //
+    // The option can be applied to the following singular field types:
+    //
+    // - any message or enum type;
+    // - any numeric type;
+    // - `bool`, `string` and `bytes`.
+    //
+    // Repeated fields, maps, and fields with explicit `optional` cardinality are not supported.
+    // Such declarations will lead to build-time errors. For more information on field cardinality,
+    // refer to the official docs: https://protobuf.dev/programming-guides/proto3/#field-labels.
+    //
+    // Assigning a value to a message field can be done in various ways in the generated code.
+    // It depends on the target language and specific implementation of `protoc`. This option
+    // doesn't enforce field immutability at the binary representation level. Also, it does not
+    // prevent the use of Protobuf utilities that can construct new messages without using field
+    // setters or properties. The primary purpose of this option is to support standard use cases,
+    // such as assigning values through setters or retrieving them during data merging.
+    //
+    // For example, let's take a look on how it works for the generated Java code. The following
+    // use cases are supported and validated by the option:
+    //
+    // 1. Assigning a field value using the field setter.
+    // 2. Assigning a field value using the field descriptor.
+    // 3. Merging data from another instance of the message class.
+    // 4. Merging data from a message's binary representation.
+    // 5. Merging specific fields (available for Message fields).
+    //
+    // Unsupported Java use cases include:
+    //
+    // 1. Constructing a message using the `DynamicMessage` class.
+    // 2. Merging data from messages provided by third-party Protobuf implementations.
+    // 3. Clearing a specific field or an entire message.
+    //
+    // For unsupported scenarios, the option performs no validation. It does not throw errors
+    // or print warnings.
+    //
+    // A typical use case involves a field, such as an ID, which remains constant throughout
+    // the lifecycle of an entity.
+    //
+    // Example: using `(set_once)` field validation constraint.
+    //
+    //     message User {
+    //         UserId id = 1 [(set_once) = true];
+    //     }
+    //
+    // Once set, the `id` field cannot be changed.
+    //
+    // Use `(if_set_again).error_msg` option to specify a custom error message that will be used for
+    // composing the error upon attempting to re-assign the field value. Refer to the documentation
+    // for the corresponding option for an example of its usage.
+    //
+    bool set_once = 73824;
+
+    // The option to enforce uniqueness for collection fields.
+    //
+    // When the option is set to `true`, the behavior is as follows:
+    //
+    // 1. For `repeated` fields: all elements must be unique.
+    // 2. For `map` fields: while the map keys are inherently unique, all associated values
+    //    must also be unique.
+    //
+    // Other field types are not supported.
+    //
+    // Uniqueness is determined by comparing the elements themselves, using their full equality.
+    // For example, in Java, it is defined by the `equals()` method. No special cases are applied,
+    // such as comparing only specific fields like IDs.
+    //
+    // Example: using `(distinct)` constraint for a `repeated` field.
+    //
+    //    message Blizzard {
+    //
+    //        // All snowflakes must be unique in this blizzard.
+    //        //
+    //        // Attempting to add a snowflake that is equal to an existing one would result
+    //        // in a constraint violation error.
+    //        //
+    //        repeated Snowflake snowflakes = 1 [(distinct) = true];
+    //    }
+    //
+    // Example: using `(distinct)` constraint for a `map` field.
+    //
+    //    message UniqueEmails {
+    //
+    //        // The associated email values must be unique.
+    //        //
+    //        // Attempting to add a key/value pair where the `Email` value duplicates
+    //        // an existing one would result in a constraint violation error.
+    //        //
+    //        map<string, Email> emails = 1 [(distinct) = true];
+    //    }
+    //
+    bool distinct = 73825;
+
+    // Reserved 73826 for deleted `range` option, which had `string` type.
+
+    // Defines the error message used if a `set_once` field is set again.
+    //
+    // Applies only to the fields marked as `set_once`.
+    //
+    IfSetAgainOption if_set_again = 73827;
+
+    // Defines the error message used if a `distinct` field has duplicates.
+    //
+    // Applies only to the repeated fields marked as `distinct`.
+    //
+    IfHasDuplicatesOption if_has_duplicates = 73828;
+
+    // The option to indicate that a numeric field is required to have a value which belongs
+    // to the specified bounded range.
+    //
+    // For unbounded ranges, please use `(min)` and `(max) options.
+    //
+    RangeOption range = 73829;
+
+    // Reserved 73830 to 73849 for future validation options.
+
+    // API Annotations
+    //-----------------
+
+    // Indicates a field which is internal to Spine, not part of the public API, and should not be
+    // used by users of the framework.
+    //
+    // If you plan to implement an extension of the framework, which is going to be
+    // wired into the framework, you may use the internal parts. Please consult with the Spine
+    // team, as the internal APIs do not have the same stability API guarantee as public ones.
+    //
+    bool internal = 73850;
+
+    // Reserved 73851 for the deleted SPI option.
+
+    // Indicates a field that can change at any time, and has no guarantee of API stability and
+    // backward-compatibility.
+    //
+    // Usage guidelines:
+    // 1. This annotation is used only on public API. Internal interfaces should not use it.
+    // 2. This annotation can only be added to new API. Adding it to an existing API is considered
+    //    API-breaking.
+    // 3. Removing this annotation from an API gives it stable status.
+    //
+    bool experimental = 73852;
+
+    // Signifies that a public API is subject to incompatible changes, or even removal, in a future
+    // release.
+    //
+    // An API bearing this annotation is exempt from any compatibility guarantees made by its
+    // containing library. Note that the presence of this annotation implies nothing about the
+    // quality of the API in question, only the fact that it is not "API-frozen."
+    // It is generally safe for applications to depend on beta APIs, at the cost of
+    // some extra work during upgrades.
+    //
+    bool beta = 73853;
+
+    // Marks an entity state field as column.
+    //
+    // The column fields are stored separately from the entity record and can be specified as
+    // filtering criteria during entity querying.
+    //
+    // The column field should be declared as follows:
+    //
+    // message UserProfile {
+    //    ...
+    //    int32 year_of_registration = 8 [(column) = true];
+    // }
+    //
+    // The `year_of_registration` field value can then be used as query parameter when reading
+    // entities of `UserProfile` type from the server side.
+    //
+    // The value of a column field can be updated in two ways:
+    //
+    // 1. In the receptors of the entity, just like any other part of entity state.
+    // 2. Using the language-specific tools like `EntityWithColumns` interface in Java.
+    //
+    // All column fields are considered optional by the framework.
+    //
+    // Currently, only entities of projection and process manager type are
+    // eligible for having columns (see `EntityOption`).
+    // For all other message types the column declarations are ignored.
+    //
+    // The `repeated` and `map` fields cannot be columns.
+    //
+    bool column = 73854;
+
+    // Reserved 73855 to 73890 for future options.
+
+    // Reserved 73900 for removed `by` option.
+}
+
+extend google.protobuf.OneofOptions {
+
+    // Deprecated: use the `(choice)` option instead.
+    bool is_required = 73891 [deprecated = true];
+
+    // Controls whether a `oneof` group must always have one of its fields set.
+    ChoiceOption choice = 73892;
+
+    // Reserved 73893 to 73899 for future options.
+}
+
+extend google.protobuf.MessageOptions {
+
+    // Validation Constraints
+    //------------------------
+
+    // The default validation error message.
+    //
+    // Please note, this option is intended for INTERNAL USE only. It applies to message types
+    // that extend `FieldOptions` and is not intended for external usage.
+    //
+    // If a validation option detects a constraint violation and no custom error message is defined
+    // for that specific option, it will fall back to the message specified by `(default_message)`.
+    //
+    // For example, here is how to declare the default message for `(goes)` option:
+    //
+    // ```
+    // message GoesOption {
+    //   // The default error message.
+    //   option (default_message) = "The field `${goes.companion}` must also be set when `${field.path}` is set.";
+    // }
+    // ```
+    //
+    // Note: The placeholders available within `(default_message)` depend solely on the particular
+    // validation option that uses it. Each option may define its own set of placeholders, or none.
+    //
+    string default_message = 73901 [(internal) = true];
+
+    // Deprecated: use the `(require)` option instead.
+    string required_field = 73902 [deprecated = true];
+
+    // See `EntityOption`.
+    EntityOption entity = 73903;
+
+    // An external validation constraint for a field.
+    //
+    // WARNING: This option is deprecated and is scheduled for removal in Spine v2.0.0.
+    //
+    // Allows to re-define validation constraints for a message when its usage as a field of
+    // another type requires alternative constraints. This includes definition of constraints for
+    // a message which does not have them defined within the type.
+    //
+    // A target field of an external constraint should be specified using a fully-qualified
+    // field name (e.g. `mypackage.MessageName.field_name`).
+    //
+    // Example: defining external validation constraint.
+    //
+    //     package io.spine.example;
+    //
+    //     // Defines a change in a string value.
+    //     //
+    //     // Both of the fields of this message are not `required` to be able to describe
+    //     // a change from empty value to non-empty value, or from a non-empty value to
+    //     // an empty string.
+    //     //
+    //     message StringChange {
+    //
+    //          // The value of the field that's changing.
+    //          string previous_value = 1;
+    //
+    //          // The new value of the field.
+    //          string new_value = 2;
+    //     }
+    //
+    //     // A command to change a name of a task.
+    //     //
+    //     // The task has a non-empty name. A new name cannot be empty.
+    //     //
+    //     message RenameTask {
+    //
+    //          // The ID of the task to rename.
+    //          string task_id = 1;
+    //
+    //          // Instruction for changing the name.
+    //          //
+    //          // The value of `change.previous_value` is the current name of the task.
+    //          // It cannot be empty.
+    //          //
+    //          // The value of `change.new_value` is the new name of the task.
+    //          // It cannot be empty either.
+    //          //
+    //          StringChange change = 1 [(validate) = true];
+    //     }
+    //
+    //     // External validation constraint for both fields of the `StringChange` message
+    //     // in the scope of the `RenameTask` command.
+    //     //
+    //     message RequireTaskNames {
+    //          option (constraint_for) = "spine.example.RenameTask.change";
+    //
+    //          string previous_value = 1 [(required) = true];
+    //          string new_value = 2 [(required) = true];
+    //     }
+    //
+    // NOTE: A target field for an external validation constraint must be have the option `(validate)`
+    //       set to `true`. See the definition of the `RenameTask.change` field in the example
+    //       above. If there is no such option defined, or it is set to `false`, the external
+    //       constraint will not be applied.
+    //
+    // External validation constraints can be applied to fields of several types.
+    // To do so, separate fully-qualified references to these fields with comma.
+    //
+    // Example: external validation constraints for multiple fields.
+    //
+    //     // External validation constraint for requiring a new value in renaming commands.
+    //     message RequireNewName {
+    //         option (constraint_for) = "spine.example.RenameTask.change,"
+    //                                  "spine.example.RenameProject.change,";
+    //                                  "spine.example.UpdateComment.text_change;
+    //
+    //         string new_value = 1 [(required) = true];
+    //     }
+    //
+    // NOTE: An external validation constraint for a field must be defined only once.
+    //       Spine Model Compiler does not check such an "overwriting".
+    //       See the issue: https://github.com/SpineEventEngine/base/issues/318.
+    //
+    string constraint_for = 73904 [deprecated = true];
+
+    // Reserved 73905 to 73910 for future validation options.
+
+    // API Annotations
+    //-----------------
+
+    // Indicates a type usage of which is restricted in one of the following ways.
+    //
+    // 1. This type is internal to the Spine Event Engine framework. It is not a part of
+    // the public API, and must not be used by framework users.
+    //
+    // 2. The type is internal to a bounded context, artifact of which exposes the type to
+    // the outside world (presumably for historical reasons).
+    //
+    // The type with such an option can be used only inside the bounded context which declares it.
+    //
+    // The type must not be used neither for inbound (i.e. being sent to the bounded context
+    // which declares this type) nor for outbound communication (i.e. being sent by this
+    // bounded context outside).
+    //
+    // An attempt to violate these usage restrictions will result in a runtime error.
+    //
+    bool internal_type = 73911;
+
+    // Indicates a file which contains elements of Service Provider Interface (SPI).
+    bool SPI_type = 73912;
+
+    // Indicates a public API that can change at any time, and has no guarantee of
+    // API stability and backward-compatibility.
+    bool experimental_type = 73913;
+
+    // Signifies that a public API is subject to incompatible changes, or even removal,
+    // in a future release.
+    bool beta_type = 73914;
+
+    // Specifies a characteristic inherent in the the given message type.
+    //
+    // Example: using `(is)` message option.
+    //
+    //     message CreateProject {
+    //         option (is).java_type = "ProjectCommand";
+    //
+    //         // Remainder omitted.
+    //     }
+    //
+    // In the example above, `CreateProject` message is a `ProjectCommand`.
+    //
+    // To specify a characteristic for every message in a `.proto` file,
+    // please use `(every_is)` file option.
+    //
+    // If both `(is)` and `(every_is)` options are applicable for a type, both are applied.
+    //
+    // When targeting Java, specify the name of a Java interface to be implemented by this
+    // message via `(is).java_type`.
+    //
+    IsOption is = 73915;
+
+    // Reserved 73916 to 73921 for future API annotation options.
+
+    // Reserved 73922 for removed `enrichment_for` option.
+
+    // Specifies the natural ordering strategy for this type.
+    //
+    // Code generators should generate language-specific comparisons based on the field paths.
+    //
+    // Runtime comparators may use the reflection API to compare field values.
+    //
+    CompareByOption compare_by = 73923;
+
+    // The constraint to require at least one of the fields or combinations of fields.
+    RequireOption require = 73924;
+
+    // Reserved 73925 to 73938 for future options.
+
+    // Reserved 73939 and 73940 for the deleted options `events` and `rejections`.
+}
+
+extend google.protobuf.FileOptions {
+
+    // Specifies a type URL prefix for all types within a file.
+    //
+    // This type URL will be used when packing messages into `Any`.
+    // See `any.proto` for more details.
+    //
+    string type_url_prefix = 73941;
+
+    // Indicates a file which contains types usage of which is restricted.
+    //
+    // For more information on such restrictions please see the documentation of
+    // the type option called `internal_type`.
+    //
+    // If a file contains a declaration of a `service`, this option will NOT be applied to it.
+    // A service is not a data type, and therefore, this option does not apply to it.
+    // Internal services are not supported.
+    //
+    bool internal_all = 73942;
+
+    // Indicates a file which contains elements of Service Provider Interface (SPI).
+    //
+    // This option applies to messages, enums, and services.
+    //
+    bool SPI_all = 73943;
+
+    // Indicates a file declaring public data type API which that can change at any time,
+    // has no guarantee of API stability and backward-compatibility.
+    //
+    // If a file contains a declaration of a `service`, this option will NOT be applied to it.
+    // A service is not a data type, and therefore, this option does not apply to it.
+    // Experimental services are not supported.
+    //
+    bool experimental_all = 73944;
+
+    // Signifies that a public data type API is subject to incompatible changes, or even removal,
+    // in a future release.
+    //
+    // If a file contains a declaration of a `service`, this option will NOT be applied to it.
+    // A service is not a data type, and therefore, this option does not apply to it.
+    // Beta services are not supported.
+    //
+    bool beta_all = 73945;
+
+    // Specifies a characteristic common for all the message types in the given file.
+    //
+    // Example: marking all the messages using the `(every_is)` file option.
+    // ```
+    //     option (every_is).java_type = "ProjectCommand";
+    //
+    //     message CreateProject {
+    //         // ...
+    //
+    //         message WithAssignee {
+    //         // ...
+    //         }
+    //     }
+    //
+    //     message DeleteProject { /*...*/ }
+    // ```
+    //
+    // In the example above, `CreateProject`, `CreateProject.WithAssignee`, and `DeleteProject`
+    // messages are `ProjectCommand`-s.
+    //
+    // To specify a characteristic for a single message, please use `(is)` message option.
+    // If both `(is)` and `(every_is)` options are applicable for a type, both are applied.
+    //
+    // When targeting Java, specify the name of a Java interface to be implemented by these
+    // message types via `(every_is).java_type`.
+    //
+    EveryIsOption every_is = 73946;
+
+    // Reserved 73947 to 73970 for future use.
+}
+
+extend google.protobuf.ServiceOptions {
+
+    // Indicates that the service is a part of Service Provider Interface (SPI).
+    bool SPI_service = 73971;
+
+    // Reserved 73971 to 73980.
+}
+
+// Reserved 73981 to 74000 for other future Spine Options numbers.
+
+//
+// Validation Option Types
+//---------------------------
+
+// Defines the error message used if a `required` field is not set.
+//
+// Applies only to the fields marked as `required`.
+//
+message IfMissingOption {
+
+    // The default error message.
+    option (default_message) = "The field `${parent.type}.${field.path}`"
+        " of the type `${field.type}` must have a non-default value.";
+
+    // A user-defined validation error format message.
+    //
+    // Use `error_msg` instead.
+    //
+    string msg_format = 1 [deprecated = true];
+
+    // A user-defined error message.
+    //
+    // The specified message may include the following placeholders:
+    //
+    // 1. `${field.path}` – the field path.
+    // 2. `${field.type}` – the fully qualified name of the field type.
+    // 3. `${parent.type}` – the fully qualified name of the validated message.
+    //
+    // The placeholders will be replaced at runtime when the error is constructed.
+    //
+    // Example: using the `(if_missing)` option.
+    //
+    //    message Student {
+    //        Name name = 1 [(required) = true,
+    //                       (if_missing).error_msg = "The `${field.path}` field is mandatory for `${parent.type}`."];
+    //    }
+    //
+    string error_msg = 2;
+}
+
+// Indicates that the numeric field must be greater than or equal to the specified value.
+//
+// The option supports all singular and repeated numeric fields.
+//
+message MinOption {
+
+    // The default error message.
+    option (default_message) = "The field `${parent.type}.${field.path}`"
+        " must be ${min.operator} ${min.value}. The passed value: `${field.value}`.";
+
+    // The string representation of the minimum field value.
+    //
+    // ## Integer and floating-point values
+    //
+    // A minimum value for an integer field must use an integer number. Specifying a decimal
+    // number is not allowed, even if it has no fractional part (e.g., `5.0` is invalid).
+    //
+    // A minimum value for a floating-point field must use a decimal separator (`.`), even if
+    // the value has no fractional part. An exponent part represented by `E` or `e`, followed
+    // by an optional sign and digits is allowed (e.g., `1.2E3`, `0.5e-2`).
+    //
+    // Example: defining minimum values for integer and floating-point fields.
+    //
+    // message Measurements {
+    //     int32 temperature = 1 [(min).value = "0"];
+    //     uint32 mass = 2 [(min).value = "5"];
+    //     float degree = 3 [(min).value = "0.0"];
+    //     double angle = 4 [(min).value = "30.0"];
+    //     float pressure = 5 [(min).value = "950.0E-2"];
+    //  }
+    //
+    // ## Field Type Limitations
+    //
+    // A minimum value must not fall below the limits of the field type.
+    //
+    // Example: invalid values that fall below the field type limits.
+    //
+    // message OverflowMeasurements {
+    //     float pressure = 1 [(min).value = "-5.5E38"]; // Falls below the `float` minimum.
+    //     uint32 mass = 2 [(min).value = "-5"]; // Falls below the `uint32` minimum.
+    // }
+    //
+    // ## Field references
+    //
+    // Instead of numeric literals, you can reference another numeric field.
+    // At runtime, the field’s value will be used as the bound. Nested fields are supported.
+    //
+    // Example: defining minimum values using field references.
+    //
+    // message Measurements {
+    //
+    //     int32 min_length = 1;
+    //     int32 length = 2 [(min).value = "min_length"];
+    //
+    //     Limits limits = 3;
+    //     int32 temperature = 4 [(min).value = "limits.min_temperature"];
+    //     float pressure = 5 [(min).value = "limits.min_pressure"];
+    // }
+    //
+    // message Limits {
+    //     int32 min_temperature = 1;
+    //     float min_pressure = 2;
+    // }
+    //
+    // Note: Field type compatibility is not required in this case; the value is
+    // automatically converted. However, only numeric fields can be referenced.
+    // Repeated and map fields are not supported.
+    //
+    string value = 1;
+
+    // Specifies if the field should be strictly greater than the specified minimum.
+    //
+    // The default value is false, i.e. the bound is inclusive.
+    //
+    bool exclusive = 2;
+
+    // A user-defined validation error format message.
+    string msg_format = 3 [deprecated = true];
+
+    // A user-defined error message.
+    //
+    // The specified message may include the following placeholders:
+    //
+    // 1. `${field.value}` - the field value.
+    // 2. `${field.path}` – the field path.
+    // 3. `${field.type}` – the fully qualified name of the field type.
+    // 4. `${parent.type}` – the fully qualified name of the validated message.
+    // 5. `${min.value}` – the specified minimum `value`. For referenced fields, the actual
+    //    field value is also printed in round brackets along with the reference itself.
+    // 6. `${min.operator}` – if `exclusive` is set to `true`, this placeholder equals to ">".
+    //    Otherwise, ">=".
+    //
+    // The placeholders will be replaced at runtime when the error is constructed.
+    //
+    string error_msg = 4;
+}
+
+// Indicates that the numeric field must be less than or equal to the specified value.
+//
+// The option supports all singular and repeated numeric fields.
+//
+message MaxOption {
+
+    // The default error message.
+    option (default_message) = "The field `${parent.type}.${field.path}`"
+        " must be ${max.operator} ${max.value}. The passed value: `${field.value}`.";
+
+    // The string representation of the maximum field value.
+    //
+    // ## Integer and floating-point values
+    //
+    // A maximum value for an integer field must use an integer number. Specifying a decimal
+    // number is not allowed, even if it has no fractional part (e.g., `5.0` is invalid).
+    //
+    // A maximum value for a floating-point field must use a decimal separator (`.`), even if
+    // the value has no fractional part. An exponent part represented by `E` or `e`, followed
+    // by an optional sign and digits is allowed (e.g., `1.2E3`, `0.5e-2`).
+    //
+    // Example: defining maximum values for integer and floating-point fields.
+    //
+    // message Measurements {
+    //     int32 temperature = 1 [(max).value = "270"];
+    //     uint32 mass = 2 [(max).value = "1200"];
+    //     float degree = 3 [(max).value = "360.0"];
+    //     double angle = 4 [(max).value = "90.0"];
+    //     float pressure = 5 [(max).value = "1050.0E-2"];
+    //  }
+    //
+    // ## Field Type Limitations
+    //
+    // A maximum value must not exceed the limits of the field type.
+    //
+    // Example: invalid values that exceed the field type limits.
+    //
+    // message OverflowMeasurements {
+    //     float pressure = 1 [(min).value = "5.5E38"]; // Exceeds the `float` maximum.
+    //     int32 mass = 2 [(min).value = "2147483648"]; // Exceeds the `int32` maximum.
+    // }
+    //
+    // ## Field references
+    //
+    // Instead of numeric literals, you can reference another numeric field.
+    // At runtime, the field’s value will be used as the bound. Nested fields are supported.
+    //
+    // Example: defining maximum values using field references.
+    //
+    // message Measurements {
+    //
+    //     int32 max_length = 1;
+    //     int32 length = 2 [(max).value = "max_length"];
+    //
+    //     Limits limits = 3;
+    //     int32 temperature = 4 [(max).value = "limits.max_temperature"];
+    //     float pressure = 5 [(max).value = "limits.max_pressure"];
+    // }
+    //
+    // message Limits {
+    //     int32 max_temperature = 1;
+    //     float max_pressure = 2;
+    // }
+    //
+    // Note: Field type compatibility is not required in this case; the value is
+    // automatically converted. However, only numeric fields can be referenced.
+    // Repeated and map fields are not supported.
+    //
+    string value = 1;
+
+    // Specifies if the field should be strictly less than the specified maximum
+    //
+    // The default value is false, i.e. the bound is inclusive.
+    //
+    bool exclusive = 2;
+
+    // A user-defined validation error format message.
+    string msg_format = 3 [deprecated = true];
+
+    // A user-defined error message.
+    //
+    // The specified message may include the following placeholders:
+    //
+    // 1. `${field.path}` – the field path.
+    // 2. `${field.value}` - the field value.
+    // 3. `${field.type}` – the fully qualified name of the field type.
+    // 4. `${parent.type}` – the fully qualified name of the validated message.
+    // 5. `${max.value}` – the specified maximum `value`. For referenced fields, the actual
+    //    field value is also printed in round brackets along with the reference itself.
+    // 6. `${max.operator}` – if `exclusive` is set to `true`, this placeholder equals to "<".
+    //    Otherwise, "<=".
+    //
+    // The placeholders will be replaced at runtime when the error is constructed.
+    //
+    string error_msg = 4;
+}
+
+// A string field value must match the given regular expression.
+//
+// This option is applicable only to string fields,
+// including those that are repeated.
+//
+// Example: using the `(pattern)` option.
+//
+//     message CreateAccount {
+//         string id = 1 [(pattern).regex = "^[A-Za-z0-9+]+$",
+//                        (pattern).error_msg = "ID must be alphanumerical in `${parent.type}`. Provided: `${field.value}`."];
+//     }
+//
+message PatternOption {
+
+    // The default error message.
+    option (default_message) = "The `${parent.type}.${field.path}` field"
+        " must match the regular expression `${regex.pattern}` (modifiers: `${regex.modifiers}`)."
+        " The passed value: `${field.value}`.";
+
+    // The regular expression that the field value must match.
+    //
+    // Please use the Java regex dialect for the syntax baseline:
+    // https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/regex/Pattern.html
+    //
+    // Note: in Java, regex patterns are not wrapped in explicit delimiters like in Perl or PHP.
+    // Instead, the pattern is provided as a string literal. Therefore, `/` symbol does not need
+    // to be escaped.
+    //
+    // The provided string literal is passed directly to the regex engine. So, it must be exactly
+    // what you would supply to the `java.util.regex.Pattern.compile()` method.
+    //
+    string regex = 1;
+
+    reserved 2;
+    reserved "flag";
+
+    // Modifiers for this pattern.
+    Modifier modifier = 4;
+
+    // A user-defined validation error format message.
+    string msg_format = 3 [deprecated = true];
+
+    // A user-defined validation error format message.
+    //
+    // The specified message may include the following placeholders:
+    //
+    // 1. `${field.path}` – the field path.
+    // 2. `${field.value}` - the field value.
+    // 3. `${field.type}` – the fully qualified name of the field type.
+    // 4. `${parent.type}` – the fully qualified name of the validated message.
+    // 5. `${regex.pattern}` – the specified regex pattern.
+    // 6. `${regex.modifiers}` – the specified modifiers, if any. For example, `[dot_all, unicode]`.
+    //
+    // The placeholders will be replaced at runtime when the error is constructed.
+    //
+    string error_msg = 5;
+
+    // Regular expression modifiers.
+    //
+    // These modifiers are specifically selected to be supported in many implementation platforms.
+    //
+    message Modifier {
+
+        // Enables the dot (`.`) symbol to match all the characters.
+        //
+        // By default, the dot does not match line break characters.
+        //
+        // May also be known in some platforms as "single line" mode and be encoded with
+        // the `s` flag.
+        //
+        bool dot_all = 1;
+
+        // Allows to ignore the case of the matched symbols.
+        //
+        // For example, this modifier is specified, string `ABC` would be a complete match for
+        // the regex `[a-z]+`.
+        //
+        // On some platforms may be represented by the `i` flag.
+        //
+        bool case_insensitive = 2;
+
+        // Enables the `^` (caret) and `$` (dollar) signs to match a start and an end of a line
+        // instead of a start and an end of the whole expression.
+        //
+        // On some platforms may be represented by the `m` flag.
+        //
+        bool multiline = 3;
+
+        // Enables matching the whole UTF-8 sequences,
+        //
+        // On some platforms may be represented by the `u` flag.
+        //
+        bool unicode = 4;
+
+        // Allows the matched strings to contain a full match to the pattern and some other
+        // characters as well.
+        //
+        // By default, a string only matches a pattern if it is a full match, i.e. there are no
+        // unaccounted for leading and/or trailing characters.
+        //
+        // This modifier is usually not represented programming languages, as the control over
+        // weather to match an entire string or only its part is provided to the user by other
+        // language means. For example, in Java, this would be the difference between methods
+        // `matches()` and `find()` of the `java.util.regex.Matcher` class.
+        //
+        bool partial_match = 5;
+    }
+}
+
+// Specifies the message to show if a validated field happens to be invalid.
+//
+// It is applicable only to fields marked with `(validate)`.
+//
+message IfInvalidOption {
+
+    // Do not specify error message for `(validate)`, it is no longer used by
+    // the validation library.
+    option deprecated = true;
+
+    // The default error message.
+    option (default_message) = "The field `${parent.type}.${field.path}` of the type"
+        " `${field.type}` is invalid. The field value: `${field.value}`.";
+
+    // A user-defined validation error format message.
+    //
+    // Use `error_msg` instead.
+    //
+    string msg_format = 1 [deprecated = true];
+
+    // A user-defined error message.
+    //
+    // The specified message may include the following placeholders:
+    //
+    // 1. `${field.path}` – the field path.
+    // 2. `${field.value}` - the field value.
+    // 3. `${field.type}` – the fully qualified name of the field type.
+    // 4. `${parent.type}` – the fully qualified name of the field declaring type.
+    //
+    // The placeholders will be replaced at runtime when the error is constructed.
+    //
+    // Example: using the `(if_invalid)` option.
+    //
+    //     message Transaction {
+    //         TransactionDetails details = 1 [(validate) = true,
+    //                                         (if_invalid).error_msg = "The `${field.path}` field is invalid."];
+    //    }
+    //
+    string error_msg = 2;
+}
+
+// Specifies that another field must be present if the option's target field is present.
+//
+// Unlike the `required_field` that handles combination of required fields, this option is useful
+// when it is needed to say that an optional field makes sense only when another optional field
+// is present.
+//
+// This option can be applied to the same field types as `(required)`, including both the
+// target field and its companion. Supported field types are:
+//
+// - Messages and enums.
+// - Repeated fields and maps.
+// - `string` and `bytes`.
+//
+// Example: requiring mutual presence of optional fields.
+//
+//    message ScheduledItem {
+//        ...
+//        spine.time.LocalDate date = 4;
+//        spine.time.LocalTime time = 5 [(goes).with = "date"];
+//    }
+//
+message GoesOption {
+
+    // The default error message.
+    option (default_message) = "The field `${goes.companion}` must also be set when `${field.path}`"
+        " is set in `${parent.type}`.";
+
+    // The name of the companion field whose presence is required for this field to be valid.
+    string with = 1;
+
+    // A user-defined validation error format message.
+    string msg_format = 2 [deprecated = true];
+
+    // A user-defined error message.
+    //
+    // The specified message may include the following placeholders:
+    //
+    // 1. `${field.path}` – the field path.
+    // 2. `${field.value}` – the field value.
+    // 3. `${field.type}` – the fully qualified name of the field type.
+    // 4. `${parent.type}` – the fully qualified name of the validated message.
+    // 5. `${goes.companion}` – the name of the companion specified in `with`.
+    //
+    // The placeholders will be replaced at runtime when the error is constructed.
+    //
+    string error_msg = 3;
+}
+
+// Defines options of a message representing a state of an entity.
+message EntityOption {
+
+    // A type of an entity for state of which the message is defined.
+    enum Kind {
+        option allow_alias = true;
+        
+        // Reserved for errors.
+        KIND_UNKNOWN = 0;
+
+        // The message is an aggregate state.
+        AGGREGATE = 1;
+
+        // The message is a state of a projection (same as "view").
+        PROJECTION = 2;
+
+        // The message is a state of a view (same as "projection").
+        VIEW = 2;
+
+        // The message is a state of a process manager.
+        PROCESS_MANAGER = 3;
+
+        // The message is a state of an entity, which is not of the type
+        // defined by other members of this enumeration.
+        ENTITY = 4;
+    }
+
+    // The type of the entity.
+    Kind kind = 1;
+
+    // The level of visibility of the entity to queries.
+    enum Visibility {
+
+        // Default visibility is different for different types of entities:
+        //  - for projections, "FULL" is default;
+        //  - for aggregates, process managers, and other entities, "NONE" is default.
+        //
+        DEFAULT = 0;
+
+        // The entity is not visible to queries.
+        NONE = 1;
+
+        // Client-side applications can subscribe to updates of entities of this type.
+        SUBSCRIBE = 2;
+
+        // Client-side applications can query this type of entities.
+        QUERY = 3;
+
+        // Client-side applications can subscribe and query this type of entity.
+        FULL = 4;
+    }
+
+    // The visibility of the entity.
+    //
+    // If not defined, the value of this option is `DEFAULT`.
+    //
+    Visibility visibility = 2;
+}
+
+// Defines a common type for message types declared in the same proto file.
+//
+// The nature of the type depends on the target programming language.
+// For example, the `java_type` property defines a name of the Java interface common
+// to all message classes generated for the proto file having this option.
+//
+// The option triggers creation of the common type if the `generate` property is set to true.
+// Otherwise, it is expected that the user provides the reference to an existing type.
+//
+message EveryIsOption {
+
+    // Enables the generation of the common type.
+    //
+    // The default value is `false`.
+    //
+    bool generate = 1;
+
+    // The reference to a Java top-level interface.
+    //
+    // The interface cannot be nested into a class or another interface.
+    // If a nested interface is provided, the code generation should fail the build process.
+    //
+    // The value may be a fully-qualified or a simple name.
+    //
+    // When a simple name is set, it is assumed that the interface belongs to
+    // the package of the generated message classes.
+    //
+    // If the value of the `generate` field is set to `false` the referenced interface must exist.
+    // Otherwise, a compilation error will occur.
+    //
+    // If the value of the `generate` field is set to `true`, the framework will
+    // generate the interface using the given name and the package as described above.
+    //
+    // The generated interface will extend `com.google.protobuf.Message` and
+    // will have no declared methods.
+    //
+    string java_type = 2;
+}
+
+// Defines additional type for a message type in which this option is declared.
+//
+// The nature of the type depends on the target programming language.
+// For example, the `java_type` property defines a name of the Java interface which
+// the generated message class will implement.
+//
+message IsOption {
+
+    // The reference to a Java top-level interface.
+    //
+    // The interface cannot be nested into a class or another interface.
+    // If a nested interface is provided, the code generation should fail the build process.
+    //
+    // The value may be a fully-qualified or a simple name.
+    //
+    // When a simple name is set, it is assumed that the interface belongs to
+    // the package of the generated message classes.
+    //
+    // The referenced interface must exist. Otherwise, a compilation error will occur.
+    //
+    string java_type = 1;
+}
+
+// Defines the way to compare two messages of the same type to one another.
+//
+// Comparisons can be used to sort values.
+//
+// See the `(compare_by)` option.
+//
+message CompareByOption {
+
+    // Field paths used for comparisons.
+    //
+    // The allowed field types are:
+    //  - any number type;
+    //  - `bool` (`false` is less than `true`);
+    //  - `string` (in the order of respective Unicode values);
+    //  - enumerations (following the order of numbers associated with each constant);
+    //  - local messages (generated within the current build) marked with `(compare_by)`;
+    //  - external messages (from dependencies), which either marked with `(compare_by)`
+    //    OR have a comparator provided in `io.spine.compare.ComparatorRegistry`.
+    //
+    // Other types are not permitted. Repeated or map fields are not permitted either.
+    // Such declarations will lead to build-time errors.
+    //
+    // To refer to nested fields, separate the field names with a dot (`.`).
+    // No fields in the path can be repeated or maps.
+    //
+    // When multiple field paths are specified, comparison is executed in the order of reference.
+    // For example, specifying `["seconds", "nanos"]` makes the comparison mechanism prioritize
+    // the `seconds` field and refer to `nanos` only when `seconds` are equal.
+    //
+    // NOTE: When comparing fields with a message type, a non-set message is always less than
+    // a set message. But if a message is set to a default value, the comparison falls back to
+    // the field-wise comparison, i.e. number values are treated as zeros, `bool` — as `false`,
+    // and so on.
+    //
+    repeated string field = 1;
+
+    // If true, the default order is reversed. For example, numbers are ordered from the greater to
+    // the lower, enums — from the last number value to the 0th value, etc.
+    bool descending = 2;
+}
+
+// Defines the error message used if a `set_once` field is set again.
+//
+// Applies only to the fields marked as `set_once`.
+//
+message IfSetAgainOption {
+
+    // The default error message.
+    option (default_message) = "The field `${parent.type}.${field.path}` of the type"
+        " `${field.type}` already has the value `${field.value}` and cannot be reassigned"
+        " to `${field.proposed_value}`.";
+
+    // A user-defined error message.
+    //
+    // The specified message may include the following placeholders:
+    //
+    // 1. `${field.path}` – the field path.
+    // 2. `${field.type}` – the fully qualified name of the field type.
+    // 3. `${field.value}` – the current field value.
+    // 4. `${field.proposed_value}` – the value, which was attempted to be set.
+    // 5. `${parent.type}` – the fully qualified name of the validated message.
+    //
+    // The placeholders will be replaced at runtime when the error is constructed.
+    //
+    // Example: using the `(set_once)` option.
+    //
+    //     message User {
+    //         UserId id = 1 [(set_once) = true,
+    //                        (if_set_again).error_msg = "A student ID is used as a permanent identifier within academic system, and cannot be re-assigned."];
+    //     }
+    //
+    string error_msg = 1;
+}
+
+// Defines the error message used if a `distinct` field has duplicates.
+//
+// Applies only to the `repeated` and `map` fields marked with the `(distinct)` option.
+//
+message IfHasDuplicatesOption {
+
+    // The default error message.
+    option (default_message) = "The field `${parent.type}.${field.path}` of the type"
+        " `${field.type}` must not contain duplicates."
+        " The duplicates found: `${field.duplicates}`.";
+
+    // A user-defined error message.
+    //
+    // The specified message may include the following placeholders:
+    //
+    // 1. `${field.path}` – the field path.
+    // 2. `${field.type}` – the fully qualified name of the field type.
+    // 3. `${field.value}` – the field value (the whole collection).
+    // 4. `${field.duplicates}` – the duplicates found (elements that occur more than once).
+    // 5. `${parent.type}` – the fully qualified name of the validated message.
+    //
+    // The placeholders will be replaced at runtime when the error is constructed.
+    //
+    // Example: using the `(distinct)` option.
+    //
+    //    message Blizzard {
+    //        repeated Snowflake = 1 [(distinct) = true,
+    //                                (if_has_duplicates).error_msg = "Every snowflake must be unique! The duplicates found: `${field.duplicates}`."];
+    //    }
+    //
+    string error_msg = 1;
+}
+
+// Indicate that the numeric field must belong to the specified bounded range.
+//
+// For unbounded ranges, please use `(min)` and `(max) options.
+//
+// The option supports all singular and repeated numeric fields.
+//
+message RangeOption {
+
+    // The default error message.
+    option (default_message) = "The field `${parent.type}.${field.path}` must be within"
+        " the following range: `${range.value}`. The passed value: `${field.value}`.";
+
+    // The string representation of the range.
+    //
+    // A range consists of two bounds: a lower bound and an upper bound. These bounds are
+    // separated by either the `..` or ` .. ` delimiter. Each bound can be either open
+    // or closed. The format of the bounds and the valid values depend on the type of field.
+    //
+    // ## Bound Types
+    //
+    // - Closed bounds include the endpoint and are indicated using square brackets (`[`, `]`).
+    //   Example: `[0..10]` represents values from 0 to 10, inclusive.
+    //
+    // - Open bounds exclude the endpoint and are indicated using parentheses (`(`, `)`).
+    //   Example: `(0..10)` represents values strictly between 0 and 10.
+    //
+    // The lower bound must be less than or equal to the upper bound.
+    //
+    // ## Integer Fields
+    //
+    // A range for an integer field must use integer numbers. Specifying a decimal number
+    // is not allowed, even if it has no fractional part (e.g., `5.0` is invalid).
+    //
+    // Example: defining ranges for integer fields.
+    //
+    // message Measurements {
+    //      int32 length = 1 [(range).value = "[0..100)"];
+    //      uint32 mass = 2 [(range).value = "(0..100]"];
+    //  }
+    //
+    // ## Floating-Point Fields
+    //
+    // A range for a floating-point field must use a decimal separator (`.`), even if the value
+    // has no fractional part. An exponent part represented by `E` or `e`, followed by an optional
+    // sign and digits is allowed (e.g., `1.2E3`, `0.5e-2`).
+    //
+    // Example: defining ranges for floating-point fields.
+    //
+    // message Measurements {
+    //     float degree = 1 [(range).value = "[0.0 .. 360.0)"];
+    //     double angle = 2 [(range).value = "(0.0 .. 180.0)"];
+    //     float pressure = 3 [(range).value = "[950.0E-2 .. 1050.0E-2]"];
+    // }
+    //
+    // ## Field Type Limitations
+    //
+    // A range must not exceed the limits of the field type.
+    //
+    // Example: invalid ranges that exceed the field type limits.
+    //
+    // message OverflowMeasurements {
+    //     float price = 1 [(range).value = "[0, 5.5E38]"]; // Exceeds the `float` maximum.
+    //     uint32 size = 2 [(range).value = "[-5; 10]"]; // Falls below the `uint32` minimum.
+    // }
+    //
+    // ## Field references
+    //
+    // Instead of numeric literals, you can reference another numeric field.
+    // At runtime, the field’s value will be used as the bound. Nested fields are supported.
+    //
+    // Example: defining ranges using field references.
+    //
+    // message Measurements {
+    //
+    //     int32 max_length = 1;
+    //     int32 length = 2 [(range).value = "[1 .. max_length"];
+    //
+    //     Limits limits = 3;
+    //     int32 temperature = 4 [(range).value = "[limits.low_temp .. limits.high_temp]"];
+    // }
+    //
+    // message Limits {
+    //     int32 low_temp = 1;
+    //     int32 high_temp = 2;
+    // }
+    //
+    // Note: Field type compatibility is not required in this case; the value is
+    // automatically converted. However, only numeric fields can be referenced.
+    // Repeated and map fields are not supported.
+    //
+    string value = 1;
+
+    // A user-defined error message.
+    //
+    // The specified message may include the following placeholders:
+    //
+    // 1. `${field.path}` – the field path.
+    // 2. `${field.value}` - the field value.
+    // 3. `${field.type}` – the fully qualified name of the field type.
+    // 4. `${parent.type}` – the fully qualified name of the validated message.
+    // 5. `${range.value}` – the specified range. For referenced fields, the actual
+    //    field value is also printed in round brackets along with the reference itself.
+    //
+    // The placeholders will be replaced at runtime when the error is constructed.
+    //
+    string error_msg = 2;
+}
+
+// Controls whether a `oneof` group must always have one of its fields set.
+//
+// Note that unlike the `(required)` constraint, this option supports any field types
+// within the group cases.
+//
+message ChoiceOption {
+
+    // The default error message.
+    option (default_message) = "The `oneof` group `${parent.type}.${group.path}` must"
+        " have one of its fields set.";
+
+    // Enables or disables the requirement for the `oneof` group to have a value.
+    bool required = 1;
+
+    // A user-defined error message.
+    //
+    // The specified message may include the following placeholders:
+    //
+    // 1. `${group.path}` – the group path.
+    // 2. `${parent.type}` – the fully qualified name of the validated message.
+    //
+    // The placeholders will be replaced at runtime when the error is constructed.
+    //
+    string error_msg = 2;
+}
+
+// Declares the field groups, at least one of which must have all of its fields set.
+//
+// Unlike the `(required)` field constraint, which requires the presence of
+// a specific field, this option allows to specify alternative field groups.
+//
+message RequireOption {
+
+    // The default error message.
+    option (default_message) = "The message `${message.type}` must have at least one of"
+        " the following field groups set: `${require.fields}`.";
+
+    // A set of field groups, at least one of which must have all of its fields set.
+    //
+    // A field group can include one or more fields joined by the ampersand (`&`) symbol.
+    // `oneof` group names are also valid and can be used along with field names.
+    // Groups are separated using the pipe (`|`) symbol.
+    //
+    // The field type determines when the field is considered set:
+    //
+    // 1. For message or enum fields, it must have a non-default instance.
+    // 2. For `string` and `bytes` fields, it must be non-empty.
+    // 3. For repeated fields and maps, it must contain at least one element.
+    //
+    // Fields of other types are not supported by this option.
+    //
+    // For `oneof`s, the restrictions above do not apply. Any `oneof` group can be used
+    // without considering the field types, and its value will be checked directly without
+    // relying on the default values of the fields within the `oneof`.
+    //
+    // Example: defining two field groups.
+    //
+    //     message PersonName {
+    //         option (require).fields = "given_name | honorific_prefix & family_name";
+    //
+    //         string honorific_prefix = 1;
+    //         string given_name = 2;
+    //         string middle_name = 3;
+    //         string family_name = 4;
+    //         string honorific_suffix = 5;
+    //     }
+    //
+    // In this example, at least `given_name` or a group of `honorific_prefix`
+    // and `family_name` fields must be set.
+    //
+    string fields = 1;
+
+    // A user-defined error message.
+    //
+    // The specified message may include the following placeholders:
+    //
+    // 1. `${message.type}` – the fully qualified name of the validated message.
+    // 2. `${require.fields}` – the specified field groups.
+    //
+    // The placeholders will be replaced at runtime when the error is constructed.
+    //
+    string error_msg = 2;
+}
diff --git a/docs/_options/time_options.proto b/docs/_options/time_options.proto
new file mode 100644
index 0000000000..bc73fe15f5
--- /dev/null
+++ b/docs/_options/time_options.proto
@@ -0,0 +1,106 @@
+/*
+ * Copyright 2025, TeamDev. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Redistribution and use in source and/or binary forms, with or without
+ * modification, must retain the above copyright notice and the following
+ * disclaimer.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+syntax = "proto3";
+
+// API Note on Packaging
+// ---------------------
+// We do not define the package for this file to allow shorter options for user-defined types.
+// This allows to write:
+//
+//      [(when).in = FUTURE];
+//
+// instead of:
+//
+//      [(spine.time.when).in = FUTURE];
+//
+
+import "spine/options.proto";
+
+option (type_url_prefix) = "type.spine.io";
+option java_package = "io.spine.time.validation";
+option java_outer_classname = "TimeOptionsProto";
+option java_multiple_files = true;
+
+import "google/protobuf/descriptor.proto";
+
+extend google.protobuf.FieldOptions {
+
+    // See `TimeOption`.
+    TimeOption when = 73819;
+}
+
+// Specifies that the field value is a point in time lying either in the future or in the past.
+//
+// Applicable to `google.protobuf.Timestamp` and types introduced in the `spine.time` package
+// that describe time-related concepts.
+//
+// Repeated fields are supported.
+//
+// Example: Using the `(when)` option.
+//
+//     message ScheduleMeeting {
+//         spine.time.ZonedDateTime start = 1 [(when).in = FUTURE];
+//     }
+//
+message TimeOption {
+
+    // The default error message.
+    option (default_message) = "The field `${parent.type}.${field.path}`"
+        " of the type `${field.type}` must be in the `${when.in}`."
+        " The encountered value: `${field.value}`.";
+
+    // Defines a restriction for the timestamp.
+    Time in = 1;
+
+    // Deprecated: please use `error_msg` instead.
+    string msg_format = 2 [deprecated = true];
+
+    // A user-defined error message.
+    //
+    // The specified message may include the following placeholders:
+    //
+    // 1. `${field.path}` – the field path.
+    // 2. `${field.value}` - the field value.
+    // 3. `${field.type}` – the fully qualified name of the field type.
+    // 4. `${parent.type}` – the fully qualified name of the validated message.
+    // 5. `${when.in}` – the specified timestamp restriction. It is either "past" or "future".
+    //
+    string error_msg = 3;
+}
+
+// This enumeration defines restriction for date/time values.
+enum Time {
+
+    // The default value (if the time option is not set).
+    TIME_UNDEFINED = 0;
+
+    // The value must be in the past.
+    PAST = 1;
+
+    // The value must be in the future.
+    FUTURE = 2;
+}
diff --git a/docs/_site/.browserslistrc b/docs/_site/.browserslistrc
new file mode 100644
index 0000000000..e996378126
--- /dev/null
+++ b/docs/_site/.browserslistrc
@@ -0,0 +1,3 @@
+> 0.5%
+last 2 versions
+not dead
diff --git a/docs/00-intro/index.md b/docs/content/00-intro/index.md
similarity index 69%
rename from docs/00-intro/index.md
rename to docs/content/00-intro/index.md
index 542f713dac..2c9dfa3ce5 100644
--- a/docs/00-intro/index.md
+++ b/docs/content/00-intro/index.md
@@ -3,30 +3,44 @@
 Spine Validation is a Protobuf-centric validation framework that generates
 type-safe validation code directly from your `.proto` definitions.  
 It allows you to describe constraints on fields, messages, and collections using
-declarative options and then automatically enforces these constraints at
-runtime.
+declarative options and then automatically enforces these constraints at runtime.
 
 The library is part of the Spine toolchain but can also be used independently
 in any Java/Kotlin backend that models data using Protocol Buffers.
 
----
+## Components
 
-## Key Capabilities
+Spine Validation consists of three main parts:
+
+1. **Validation plugin to Spine Compiler** – analyzes your Protobuf definitions and
+   generates validation code for messages and builders.
+
+2. **Gradle plugin** – integrates with your build, configuring Spine Compiler to run
+   the Validation code generation as part of the Protobuf compilation process.
+
+3. **Runtime library** – provides validation APIs and error reporting mechanisms
+   for JVM projects (Java and Kotlin).
+
+Together, these components enable declarative, type-safe validation that is enforced
+both at compile time and at runtime.
+
+## Key capabilities
+
+### Declarative constraints in `.proto`
 
-### 🔹 Declarative constraints in `.proto`
 Validation rules are expressed as Protobuf options such as:
 
-- `required`
-- `min` / `max`
-- `pattern`
-- `when.in = PAST | FUTURE`
+- `(required)`
+- `(min)` / `(max)`
+- `(pattern)`
 - cross-field rules and message-level constraints
 
 This keeps validation close to the data model and ensures it evolves together
 with it.
 
-### 🔹 Generated validators
-The Spine compiler plugin processes your Protobuf model and generates:
+### Generated validation code
+
+The validation plugin to Spine Compiler processes your Protobuf model and generates:
 
 - validation code for messages and builders,
 - runtime checks,
@@ -34,7 +48,7 @@ The Spine compiler plugin processes your Protobuf model and generates:
 
 No manual validators, reflection, or annotations are required.
 
-### 🔹 Runtime validation API
+### Runtime validation API
 Every generated message can be validated at runtime via:
 
 - `validate()`,
@@ -44,15 +58,16 @@ Every generated message can be validated at runtime via:
 Errors are represented as structured diagnostics suitable for API responses,
 logs, or domain exception flows.
 
-### 🔹 Rich domain-oriented constraints
+### Rich domain-oriented constraints
+
 Beyond simple “required/min/max”, the library includes:
 
-- collection rules (`distinct`, `non_empty`),
+- collection rules (`(distinct)`, `(required)`),
 - nested and cross-field validation,
-- advanced string formats (using regex),
-- temporal constraints (`PAST`, `FUTURE`).
+- advanced string formats (using regex).
+
+### Extensible architecture
 
-### 🔹 Extensible architecture
 Teams can define custom validation options by:
 
 - declaring new `.proto` options,
@@ -61,9 +76,8 @@ Teams can define custom validation options by:
 
 This allows entire organizations to standardize domain validation rules.
 
----
 
-## When to Use Spine Validation
+## When to use Spine Validation
 
 Use Spine Validation if:
 
@@ -76,11 +90,10 @@ Use Spine Validation if:
 It is especially useful in:
 
 - backend services (Java/Kotlin),
-- event-driven and CQRS systems,
+- message-driven systems,
 - systems with rich domain models,
 - multi-service environments where shared `.proto` models are common.
 
----
 
 ## Relationship to the Spine Event Engine
 
@@ -97,9 +110,8 @@ framework’s error reporting mechanisms.
 However, the library is fully standalone and can be used without the rest of the
 Spine stack.
 
----
 
-## What’s Next
+## What's next
 
 - [Target Audience](target-audience.md)
 - [Philosophy](philosophy.md)
diff --git a/docs/00-intro/philosophy.md b/docs/content/00-intro/philosophy.md
similarity index 81%
rename from docs/00-intro/philosophy.md
rename to docs/content/00-intro/philosophy.md
index 31c5384de4..ea6528686e 100644
--- a/docs/00-intro/philosophy.md
+++ b/docs/content/00-intro/philosophy.md
@@ -5,9 +5,8 @@ model, generate, and enforce constraints on their data.
 This section outlines those principles and explains why the library is designed
 the way it is.
 
----
 
-## 1. Validation Belongs to the Model
+## 1. Validation belongs to the model
 
 In many systems, validation rules drift between:
 
@@ -32,11 +31,10 @@ By placing constraints in `.proto` definitions, validation becomes:
 This prevents the typical “broken windows” of duplicated or inconsistent
 validation logic.
 
----
 
-## 2. Generated Code Over Reflection
+## 2. Generated code over reflection
 
-Reflection-based frameworks (Bean Validation, etc.) are convenient but come with:
+Reflection-based frameworks (Jakarta Validation, etc.) are convenient but come with:
 
 - runtime penalties,
 - fragile metadata conventions (annotations, naming),
@@ -50,18 +48,18 @@ Benefits:
 - fast, predictable runtime without reflection,
 - validation logic is type-safe,
 - errors in validation configuration are caught early,
-- generated validators integrate naturally into the Protobuf builder model.
+- generated validation code integrates naturally into the Protobuf builder model.
 
 This approach scales better for complex domain models or high-throughput services.
 
----
-
-## 3. Declarative, Not Imperative
+## 3. Declarative, not imperative
 
 Validation is expressed declaratively through Protobuf options:
 
 ```proto
-string email = 1 [(pattern).email = true, (required) = true];
+message Name {
+    string value = 1 [(required) = true, (pattern).regex = "^[A-Za-z ]+$"];
+}
 ```
 Declarative rules:
  * are concise,
@@ -72,7 +70,7 @@ Declarative rules:
 
 Developers describe intent, and the library handles implementation.
 
-## 4. Predictability and Consistency
+## 4. Predictability and consistency
 
 Validation should behave the same regardless of:
 
@@ -91,18 +89,17 @@ Given the same inputs, you always get the same:
 Consistency is especially important in distributed systems and domain-driven
 design contexts.
 
-## 5. Domain-Oriented Constraints
+## 5. Domain-oriented constraints
 
-Instead of focusing only on primitive checks (min/max, required), the library
+Instead of focusing only on primitive checks (`min`/`max`, `required`), the library
 embraces **domain semantics**, such as:
 
- * temporal rules (past, future),
  * cross-field logic,
  * nested validation,
  * constraints on identity fields,
  * collection semantics.
 
-## 6. Extensibility as a First-Class Feature
+## 6. Extensibility as a first-class feature
 
 Spine Validation is extensible via:
 
@@ -113,7 +110,7 @@ Spine Validation is extensible via:
 This makes the library a foundation for building consistent validation standards
 across teams and services.
 
-## 7. No UI or Presentation Layer Concerns
+## 7. No UI or presentation layer concerns
 
 Spine Validation intentionally does not attempt to validate UI forms,
 front-end models, or JSON schemas.
@@ -121,7 +118,7 @@ front-end models, or JSON schemas.
 Its focus is entirely on:
 
 ```
-Protobuf → generated Java/Kotlin → domain logic
+Protobuf → generated Java/Kotlin/TypeScript → domain logic
 ```
 
 Everything else (frontend validation, OpenAPI, view models) should build on top
diff --git a/docs/00-intro/target-audience.md b/docs/content/00-intro/target-audience.md
similarity index 85%
rename from docs/00-intro/target-audience.md
rename to docs/content/00-intro/target-audience.md
index ad707be8da..caa8e06261 100644
--- a/docs/00-intro/target-audience.md
+++ b/docs/content/00-intro/target-audience.md
@@ -1,4 +1,4 @@
-# Target Audience
+# Target audience
 
 Spine Validation is designed for developers who model data and APIs using
 **Protocol Buffers** and need a structured, type-safe way to express and enforce
@@ -6,9 +6,7 @@ constraints on that data.
 
 The library serves several overlapping groups:
 
----
-
-## 1. Application Developers
+## 1. Application developers
 
 Developers building backend services in **Java** or **Kotlin** who need
 validation for:
@@ -27,9 +25,7 @@ These developers benefit from:
 This group typically works directly with generated message builders and calls
 `validate()` at appropriate points in their workflow.
 
----
-
-## 2. Teams Using the Spine Event Engine
+## 2. Teams using the Spine Event Engine
 
 Spine Validation is the standard validation mechanism used inside the
 **Spine Event Engine**.  
@@ -43,12 +39,10 @@ validate:
 For Spine users, this library provides:
 
 - consistent validation semantics across the entire model,
-- rich temporal and domain-focused constraints,
+- rich domain-focused constraints,
 - cross-field and message-level validations.
 
----
-
-## 3. Framework and Platform Integrators
+## 3. Framework and platform integrators
 
 Engineers who build frameworks, platforms, or infrastructure around Protobuf
 often need to enforce rules across:
@@ -65,12 +59,9 @@ For these integrators, Spine Validation provides:
 - hooks for custom validators,
 - extension points via custom validation options.
 
----
-
-## 4. Library Authors and Tooling Developers
+## 4. Library authors and tooling developers
 
-Those who extend `protoc`, build code-gen pipelines, or maintain shared data
-models across a large organization can use Spine Validation to:
+Those who maintain shared data models across a large organization can use Spine Validation to:
 
 - standardize validation behavior for all services,
 - define custom domain-specific validation options,
@@ -82,9 +73,8 @@ This group interacts with advanced parts of the library such as:
 - option policies,
 - custom code generation units.
 
----
 
-## 5. Not the Target Audience (Explicitly)
+## 5. Not the target audience (explicitly)
 
 The library is **not** designed for:
 
@@ -96,7 +86,6 @@ The library is **not** designed for:
 Spine Validation is intentionally focused on the **Protobuf → runtime code**
 pipeline and the domain layer of applications.
 
----
 
 ## Summary
 
diff --git a/docs/content/01-getting-started/adding-to-build.md b/docs/content/01-getting-started/adding-to-build.md
new file mode 100644
index 0000000000..3f2ceca970
--- /dev/null
+++ b/docs/content/01-getting-started/adding-to-build.md
@@ -0,0 +1,58 @@
+# Adding Validation to a Gradle build
+
+Spine Validation can be added to a JVM project in two different ways.
+Choose the setup that matches your project:
+
+- Standalone use in any Protobuf-based project.
+- As part of a Spine-based project that already uses the CoreJvm toolchain.
+
+Both modes integrate the Validation compiler into the build and add the runtime library.
+
+
+## Mode 1: Standalone via Validation Gradle Plugin
+
+Use this mode if you want to run Validation without the rest of Spine.
+
+1) Add the Validation plugin to the build.
+
+```kotlin
+plugins {
+    id("io.spine.validation") version "<spine-version>"
+}
+```
+
+2) Make sure your repositories include Spine artifacts (the same repositories you use
+   for other Spine tools and libraries).
+
+3) Optional: control Validation generation explicitly.
+
+```kotlin
+spine {
+   validation {
+       enabled.set(true) // `true` by default
+   }
+}
+```
+
+The plugin wires Validation into Spine Compiler, adds the Validation Java codegen bundle,
+and brings in the JVM runtime dependency automatically.
+
+
+## Mode 2: Spine-based project via CoreJvm Gradle Plugin
+
+If your project is base on the Spine CoreJvm library, apply the CoreJvm Gradle plugin instead of
+adding Validation directly. CoreJvm brings in the Validation Gradle plugin for you.
+
+```kotlin
+plugins {
+    id("io.spine.core-jvm") version "<spine-version>"
+}
+```
+
+Validation is available right away, and you can configure it using the same `validation`
+extension if needed.
+
+
+## Next step
+
+Continue with [Your first validated model](first-model.md).
diff --git a/docs/content/01-getting-started/first-model.md b/docs/content/01-getting-started/first-model.md
new file mode 100644
index 0000000000..15e820cc14
--- /dev/null
+++ b/docs/content/01-getting-started/first-model.md
@@ -0,0 +1,93 @@
+# Your first validated model
+
+This guide shows how to define a Protobuf model with validation rules and how those
+rules are enforced in the generated JVM code.
+
+The validation options come from `spine/options.proto` and include constraints like
+`(required)`, `(min)`, `(max)`, `(pattern)`, `(distinct)`, and `(validate)`.
+
+
+## 1) Define a validated message
+
+Create a `.proto` file and import the validation options you need:
+
+```protobuf
+syntax = "proto3";
+
+package spine.validation.docs.first_model;
+
+import "spine/options.proto";
+
+option java_package = "io.spine.validation.docs.firstmodel";
+option java_multiple_files = true;
+
+// Provides bank card information with validation rules.
+//
+// The digits of the card are simplified for the sake of the example.
+//
+message BankCard {
+    // Must be present and match a simple card pattern.
+    string digits = 1 [
+        (required) = true,
+        (pattern).regex = "^\\d{4}(?: \\d{4}){3}"
+    ];
+
+    // Must be present and contain at least 4 Latin letters or spaces.
+    string owner = 2 [
+        (required) = true,
+        (pattern).regex = "^[A-Z](?:[A-Za-z ]{2,}[a-z])$"
+    ];
+
+    // All tags must be unique. Tags are optional.
+    repeated string tags = 3 [
+        (distinct) = true
+    ];
+}
+```
+
+Notes on the options used:
+
+- `(required)` ensures the field is set and not default or empty.
+- `(pattern).regex` validates string contents with a regular expression.
+- `(distinct)` enforces uniqueness in `repeated` and `map` fields.
+
+
+## 2) Build the project
+
+Run your Gradle build as usual. The Validation Gradle plugin integrates with Spine Compiler
+and injects validation checks into the generated Java code.
+
+
+## 3) Use the generated validation
+
+Validation runs on `build()` and can be triggered manually with `validate()`.
+
+```java
+var card = BankCard.newBuilder()
+    .setDigits("invalid")
+    .setOwner("Al")
+    .build(); // Throws `ValidationException`.
+```
+
+```kotlin
+val card = bankCard {
+    digits = "invalid"
+    owner = "Al"
+} // Throws `ValidationException`.
+```
+
+To validate without throwing, use `validate()` on a built message:
+
+```java
+var card = BankCard.newBuilder()
+    .setDigits("invalid")
+    .buildPartial();
+
+var error = card.validate();
+error.ifPresent(err -> System.out.println(err.getMessage()));
+```
+   
+
+## What’s next
+
+Continue with [Validation Workflow](workflow.md).
diff --git a/docs/01-getting-started/index.md b/docs/content/01-getting-started/index.md
similarity index 51%
rename from docs/01-getting-started/index.md
rename to docs/content/01-getting-started/index.md
index 9ed40dde89..8e9279f293 100644
--- a/docs/01-getting-started/index.md
+++ b/docs/content/01-getting-started/index.md
@@ -1,13 +1,13 @@
-# Getting Started
+# Getting started
 
-This section helps you set up Spine Validation, define your first validated Protobuf model, and see validation in action in Java and Kotlin.
+This section helps you set up Spine Validation, define your first validated Protobuf model,
+and see validation in action in Java and Kotlin.
 
 If you are new to the library, read the short overview first:
 - Introduction → [Overview](../00-intro/index.md)
-- Who this is for → [Target Audience](../00-intro/target-audience.md)
+- Who this is for → [Target audience](../00-intro/target-audience.md)
 - Design principles → [Philosophy](../00-intro/philosophy.md)
 
----
 
 ## What you’ll learn
 
@@ -20,32 +20,32 @@ If you are new to the library, read the short overview first:
 - Java 17+
 - Gradle (Kotlin DSL or Groovy)
 - Protobuf compiler (`protoc`)
-- Optional: Kotlin 2.2.20+ for the Kotlin Protobuf DSL
+- Optional: Kotlin 2.2.21+ for the Kotlin Protobuf DSL
 
-If your project already generates Java/Kotlin sources from `.proto` files, you’re 90% there. Spine Validation integrates into the build to generate and inject validation logic into the code produced by `protoc`.
+If your project already generates Java/Kotlin sources from `.proto` files, you’re 90% there.
+Spine Validation integrates into the build to generate and inject validation logic into
+the code produced by `protoc`.
 
----
 
 ## Quick path
 
-1) Install the library and compiler integration
-- Follow [Installation](installation.md) to add the necessary repositories and build configuration.
-- If you use a custom Protobuf setup, see [Compiler Configuration](../05-configuration/compiler.md).
+1) Add Spine Validation to your Gradle build
+- Follow the [instructions](adding-to-build.md).
 
 2) Define constraints in your `.proto` files
-- Import `spine/options.proto` (and `spine/time_options.proto` for temporal constraints).
-- Add declarative options like `(required)`, `(min)`, `(pattern)`, `(when).in = PAST`.
+- Import `spine/options.proto`.
+- Add declarative options like `(required)`, `(min)`, `(pattern)`.
 
 3) Build your project
-- The Spine compiler plugin scans your model and generates validation code.
+- The Validation plugin to Spine Compiler scans your model and generates validation code.
 
 4) Use the generated API
-- Validate on builder `build()` or call `validate()` explicitly. See [Your First Validated Model](first-model.md).
+- Validate on builder `build()` or call `validate()` explicitly.
+  See [Your first validated model](first-model.md).
 
----
 
 ## What’s next
 
-- [Installation](installation.md)
+- [Adding Validation to your build](adding-to-build.md)
 - [Your First Validated Model](first-model.md)
 - [Validation Workflow](workflow.md)
diff --git a/docs/content/ToC.md b/docs/content/ToC.md
new file mode 100644
index 0000000000..bca994db07
--- /dev/null
+++ b/docs/content/ToC.md
@@ -0,0 +1,76 @@
+# Spine Validation — Table of contents
+
+## Introduction
+- [Overview](00-intro/index.md)
+- [Target audience](00-intro/target-audience.md)
+- [Philosophy](00-intro/philosophy.md)
+
+## 1. Getting started
+- [Getting started](01-getting-started/index.md)
+- [Adding Validation to a Gradle build](01-getting-started/adding-to-build.md)
+- [Your first validated model](01-getting-started/first-model.md)
+- [Validation workflow](01-getting-started/workflow.md)
+
+## 2. Concepts
+- [Concepts overview](02-concepts/index.md)
+- [Validation options overview](02-concepts/options-overview.md)
+- [The validation engine](02-concepts/validation-engine.md)
+- [Integration with Protobuf & Spine Compiler](02-concepts/protobuf-integration.md)
+
+## 3. Built-in validation options
+- [Built-in options overview](03-built-in-options/index.md)
+
+### 3.1. Field constraints
+- [Overview](03-built-in-options/fields/index.md)
+- [required](03-built-in-options/fields/required.md)
+- [pattern](03-built-in-options/fields/pattern.md)
+- [min/max](03-built-in-options/fields/min-max.md)
+- [range](03-built-in-options/fields/range.md)
+- [length/size](03-built-in-options/fields/length-size.md)
+- [unique](03-built-in-options/fields/unique.md)
+
+### 3.2. String constraints
+- [Overview](03-built-in-options/strings/index.md)
+- [Advanced patterns](03-built-in-options/strings/pattern-advanced.md)
+
+### 3.3. Numeric constraints
+- [Overview](03-built-in-options/numbers/index.md)
+- [Numeric bounds](03-built-in-options/numbers/numeric-bounds.md)
+
+### 3.4. Collection constraints
+- [Overview](03-built-in-options/collections/index.md)
+- [`(required)`](03-built-in-options/collections/required.md)
+- [`(distinct)`](03-built-in-options/collections/distinct.md)
+- [Collection size](03-built-in-options/collections/collection-size.md)
+
+### 3.5. Message-level constraints
+- [Overview](03-built-in-options/message/index.md)
+- [required_for](03-built-in-options/message/required-for.md)
+- [Nested validation](03-built-in-options/message/nested-validation.md)
+- [Cross-field validation](03-built-in-options/message/cross-field.md)
+
+## 4. Using validation in code
+- [Overview](04-using-validation/index.md)
+- [Validating messages](04-using-validation/validating-messages.md)
+- [Handling errors](04-using-validation/handling-errors.md)
+- [Kotlin usage](04-using-validation/kotlin-usage.md)
+- [Framework integration](04-using-validation/framework-integration.md)
+
+## 5. Extending validation
+- [Overview](06-extending/index.md)
+- [Architecture](06-extending/architecture.md)
+- [Custom validation options](06-extending/custom-options.md)
+- [Custom runtime validators](06-extending/custom-runtime-validators.md)
+
+## 6. Recipes (cookbook)
+- [Overview](07-recipes/index.md)
+- [Domain IDs](07-recipes/domain-ids.md)
+- [Common cases](07-recipes/common-cases.md)
+- [Cross-field logic](07-recipes/cross-field-logic.md)
+- [API validation](07-recipes/api-validation.md)
+
+## 7. Reference
+- [Reference overview](08-reference/index.md)
+- [List of validation options](08-reference/options.md)
+- [Java/Kotlin API index](08-reference/api.md)
+- [Glossary](08-reference/glossary.md)
diff --git a/docs/adding-custom-validation.md b/docs/content/adding-custom-validation.md
similarity index 100%
rename from docs/adding-custom-validation.md
rename to docs/content/adding-custom-validation.md
diff --git a/docs/developers-guide/architecture.md b/docs/content/developers-guide/architecture.md
similarity index 100%
rename from docs/developers-guide/architecture.md
rename to docs/content/developers-guide/architecture.md
diff --git a/docs/developers-guide/key-modules.md b/docs/content/developers-guide/key-modules.md
similarity index 96%
rename from docs/developers-guide/key-modules.md
rename to docs/content/developers-guide/key-modules.md
index 4de498a725..f0d6b9bfc1 100644
--- a/docs/developers-guide/key-modules.md
+++ b/docs/content/developers-guide/key-modules.md
@@ -1,5 +1,5 @@
 
-### Key Modules
+### Key modules
 
 | Module    | Description                                                          |
 |-----------|----------------------------------------------------------------------|
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
index f8e1ee3125..61285a659d 100644
Binary files a/gradle/wrapper/gradle-wrapper.jar and b/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 23449a2b54..19a6bdeb84 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-9.2.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.3.0-bin.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME
diff --git a/java/src/main/kotlin/io/spine/tools/validation/java/JavaValidationPlugin.kt b/java/src/main/kotlin/io/spine/tools/validation/java/JavaValidationPlugin.kt
index fdd9c17afb..4187a6ce1c 100644
--- a/java/src/main/kotlin/io/spine/tools/validation/java/JavaValidationPlugin.kt
+++ b/java/src/main/kotlin/io/spine/tools/validation/java/JavaValidationPlugin.kt
@@ -71,9 +71,9 @@ private val customOptions: List<ValidationOption> by lazy {
  * Dynamically discovered instances of custom
  * [MessageValidator][io.spine.validation.MessageValidator]s.
  *
- * Please note that the KSP module is responsible for the actual discovering
- * of the message validators. The discovered validators are written to a text file
- * in the KSP task output. This property loads the validators from that file.
+ * Note that the KSP module is responsible for the actual discovering of the message validators.
+ * The discovered validators are written to a text file in the KSP task output.
+ * This property loads the validators from that file.
  */
 private val customValidators: Map<MessageClass, ValidatorClass> by lazy {
     val workingDir = System.getProperty("user.dir")
diff --git a/java/src/main/kotlin/io/spine/tools/validation/java/setonce/SetOnceBytesField.kt b/java/src/main/kotlin/io/spine/tools/validation/java/setonce/SetOnceBytesField.kt
index 668383f1b6..b79a8940af 100644
--- a/java/src/main/kotlin/io/spine/tools/validation/java/setonce/SetOnceBytesField.kt
+++ b/java/src/main/kotlin/io/spine/tools/validation/java/setonce/SetOnceBytesField.kt
@@ -38,8 +38,7 @@ import io.spine.tools.psi.java.method
 /**
  * Renders Java code to support `(set_once)` option for the given byte array [field].
  *
- * Please note, in the generated Java code, Protobuf uses [ByteString] to represent
- * an array of bytes.
+ * Note that Protobuf uses [ByteString] to represent an array of bytes in the generated code.
  *
  * @param field The byte array field that declared the option.
  * @param typeSystem The type system to resolve types.
diff --git a/java/src/main/kotlin/io/spine/tools/validation/java/setonce/SetOnceEnumField.kt b/java/src/main/kotlin/io/spine/tools/validation/java/setonce/SetOnceEnumField.kt
index 43361debc2..456deccdc6 100644
--- a/java/src/main/kotlin/io/spine/tools/validation/java/setonce/SetOnceEnumField.kt
+++ b/java/src/main/kotlin/io/spine/tools/validation/java/setonce/SetOnceEnumField.kt
@@ -39,8 +39,7 @@ import io.spine.tools.psi.java.method
 /**
  * Renders Java code to support `(set_once)` option for the given enum [field].
  *
- * Please note, in the generated Java code, Protobuf uses an ordinal number
- * to represent the currently set enum constant.
+ * Note that code generated by Protobuf uses an ordinal number to represent the currently set enum constant.
  *
  * @param field The enum field that declared the option.
  * @param typeSystem The type system to resolve types.
diff --git a/jvm-runtime/build.gradle.kts b/jvm-runtime/build.gradle.kts
index 8be6a6b4ec..2614f4bd11 100644
--- a/jvm-runtime/build.gradle.kts
+++ b/jvm-runtime/build.gradle.kts
@@ -68,7 +68,7 @@ dependencies {
     annotationProcessor(AutoService.processor)
     compileOnly(AutoService.annotations)
 
-    implementation(Base.lib)
+    api(Base.lib)
 
     testImplementation(TestLib.lib)
 }
diff --git a/jvm-runtime/src/main/kotlin/io/spine/validation/MessageValidator.kt b/jvm-runtime/src/main/kotlin/io/spine/validation/MessageValidator.kt
index df147b202a..2b534fe50d 100644
--- a/jvm-runtime/src/main/kotlin/io/spine/validation/MessageValidator.kt
+++ b/jvm-runtime/src/main/kotlin/io/spine/validation/MessageValidator.kt
@@ -82,7 +82,7 @@ import io.spine.annotation.SPI
  * }
  * ```
  *
- * Please note that standalone instances of [M] and fields of [M] type that occur in
+ * Note that standalone instances of [M] and fields of [M] type that occur in
  * other external messages **will not be validated**.
  *
  * Consider the following example:
diff --git a/jvm-runtime/src/main/proto/spine/validation/validation_error.proto b/jvm-runtime/src/main/proto/spine/validation/validation_error.proto
index 093d38e0a5..c9562d093e 100644
--- a/jvm-runtime/src/main/proto/spine/validation/validation_error.proto
+++ b/jvm-runtime/src/main/proto/spine/validation/validation_error.proto
@@ -72,7 +72,7 @@ message ConstraintViolation {
     // Example:
     //
     // ```
-    // message Student {
+    // message AddressBook {
     //     Contacts contacts = 1 [(validate) = true];
     // }
     //
@@ -85,8 +85,8 @@ message ConstraintViolation {
     // }
     // ```
     //
-    // When the `Student` message is validated and the `value` field in the nested `Email`
-    // message is invalid, this property will contain the `Student` type name, not `Email`.
+    // When the `AddressBook` message is validated and the `value` field in the nested `Email`
+    // message is invalid, this property will contain the `AddressBook` type name, not `Email`.
     // This is so because this type is an entry point to the nested validation.
     //
     string type_name = 7;
diff --git a/pom.xml b/pom.xml
index 8b9da9273d..8859a27d9e 100644
--- a/pom.xml
+++ b/pom.xml
@@ -10,7 +10,7 @@ all modules and does not describe the project structure per-subproject.
  -->
 <groupId>io.spine.tools</groupId>
 <artifactId>validation</artifactId>
-<version>2.0.0-SNAPSHOT.393</version>
+<version>2.0.0-SNAPSHOT.394</version>
 
 <inceptionYear>2015</inceptionYear>
 
@@ -62,7 +62,7 @@ all modules and does not describe the project structure per-subproject.
   <dependency>
     <groupId>io.spine</groupId>
     <artifactId>spine-validation-jvm-runtime</artifactId>
-    <version>2.0.0-SNAPSHOT.392</version>
+    <version>2.0.0-SNAPSHOT.393</version>
     <scope>compile</scope>
   </dependency>
   <dependency>
@@ -281,12 +281,12 @@ all modules and does not describe the project structure per-subproject.
   <dependency>
     <groupId>io.spine.tools</groupId>
     <artifactId>core-jvm-gradle-plugins</artifactId>
-    <version>2.0.0-SNAPSHOT.050</version>
+    <version>2.0.0-SNAPSHOT.051</version>
   </dependency>
   <dependency>
     <groupId>io.spine.tools</groupId>
     <artifactId>core-jvm-routing</artifactId>
-    <version>2.0.0-SNAPSHOT.050</version>
+    <version>2.0.0-SNAPSHOT.051</version>
   </dependency>
   <dependency>
     <groupId>io.spine.tools</groupId>
@@ -301,7 +301,7 @@ all modules and does not describe the project structure per-subproject.
   <dependency>
     <groupId>io.spine.tools</groupId>
     <artifactId>validation-java-bundle</artifactId>
-    <version>2.0.0-SNAPSHOT.392</version>
+    <version>2.0.0-SNAPSHOT.393</version>
   </dependency>
   <dependency>
     <groupId>net.sourceforge.pmd</groupId>
@@ -316,7 +316,7 @@ all modules and does not describe the project structure per-subproject.
   <dependency>
     <groupId>org.jacoco</groupId>
     <artifactId>org.jacoco.agent</artifactId>
-    <version>0.8.13</version>
+    <version>0.8.14</version>
   </dependency>
   <dependency>
     <groupId>org.jacoco</groupId>
diff --git a/proto/configuration/src/main/proto/spine/validation/config.proto b/proto/configuration/src/main/proto/spine/validation/config.proto
deleted file mode 100644
index 704e2fbbd9..0000000000
--- a/proto/configuration/src/main/proto/spine/validation/config.proto
+++ /dev/null
@@ -1,46 +0,0 @@
-syntax = "proto3";
-
-package spine.validation;
-
-option java_package = "io.spine.validation";
-option java_outer_classname = "ConfigProto";
-option java_multiple_files = true;
-
-import "spine/compiler/file_pattern.proto";
-
-// The container type for the validation config.
-//
-// ProtoData supports multiple configurations merges into a single object. In order for
-// the Validation library to be satisfied with the config, it must always have
-// the `message_markers` field of type `spine.validation.MessageMarkers`.
-//
-message ValidationConfig {
-
-    MessageMarkers message_markers = 1;
-}
-
-// The markers that define special kinds of messages.
-message MessageMarkers {
-
-    // Names of options used to mark entity state messages.
-    //
-    // For example, `["entity", "view"]`.
-    //
-    repeated string entity_option_name = 1;
-
-    // File patterns of files where entity state messages are defined.
-    //
-    // Deprecated: entity states are defined by the `entity` option, not
-    // by a file pattern.
-    //
-    repeated compiler.FilePattern entity_pattern = 2 [deprecated = true];
-
-    // File patterns of files where event messages are defined.
-    repeated compiler.FilePattern event_pattern = 3;
-
-    // File patterns of files where command messages are defined.
-    repeated compiler.FilePattern command_pattern = 4;
-
-    // File patterns of files where rejection messages are defined.
-    repeated compiler.FilePattern rejection_pattern = 5;
-}
diff --git a/tests/consumer/src/test/kotlin/io/spine/validation/test/CurrencyOptionITest.kt b/tests/consumer/src/test/kotlin/io/spine/validation/test/CurrencyOptionITest.kt
index 3d6d8250c7..6d9a5a57a2 100644
--- a/tests/consumer/src/test/kotlin/io/spine/validation/test/CurrencyOptionITest.kt
+++ b/tests/consumer/src/test/kotlin/io/spine/validation/test/CurrencyOptionITest.kt
@@ -35,7 +35,7 @@ import org.junit.jupiter.api.Test
  * by [CurrencyOption] in the `:java-tests:extensions` module.
  *
  * The `extensions` module declares the `(currency)` message option, which is used by
- * money data types in this module. Please see `main/proto/test/money.proto` for details.
+ * money data types in this module. See `main/proto/test/money.proto` for details.
  *
  * This test verifies that custom validation code works as expected.
  */
diff --git a/version.gradle.kts b/version.gradle.kts
index dc55d8b2ab..bae585a6c9 100644
--- a/version.gradle.kts
+++ b/version.gradle.kts
@@ -29,4 +29,4 @@
  *
  * For Spine-based dependencies please see [io.spine.dependency.local.Spine].
  */
-val validationVersion by extra("2.0.0-SNAPSHOT.393")
+val validationVersion by extra("2.0.0-SNAPSHOT.394")